SELINA Solutions for Class 10 Maths Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume)

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Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume) Exercise Ex. 20(A)

Question 1

The height of a circular cylinder is 20 cm and the radius of its base is 7 cm. Find :

(i) the volume

(ii) the total surface area.

Solution 1

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 2

The inner radius of a pipe is 2.1 cm. How much water can 12 m of this pipe hold?

Solution 2

Inner radius of pipe = 2.1 cm

Length of the pipe = 12 m = 1200 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 3

A cylinder of circumference 8 cm and length 21 cm rolls without sliding for Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumeseconds at the rate of 9 complete rounds per second. Find

(i) distance travelled by the cylinder in Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumeseconds, and

(ii) the area covered by the cylinder in Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumeseconds

Solution 3

Circumference of cylinder = 8 cm

Therefore, radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Length of the cylinder (h)= 21 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(i) If distance covered in one revolution is 8 cm, then distance covered in 9 revolutions = 9 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 8 = 72 cm or distance covered in 1 second = 72 cm.

Therefore, distance covered in Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumeseconds = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Curved surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area covered in one revolution = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area covered in 9 revolutions = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, area covered in 1 second = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, area covered in Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumeseconds = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 4

How many cubic meters of earth must be dug out to make a well 28 m deep and 2.8 m in diameter? Also, find the cost of plastering its inner surface at Rs 4.50 per sq meter.

Solution 4

Radius of the well = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Depth of the well = 28 m

Therefore, volume of earth dug out = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area of curved surface = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Cost of plastering at the rate of Rs 4.50 per sq m

= Rs 246.40 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 4.50

= Rs 1108.80

Question 5

What length of solid cylinder 2 cm in diameter must be taken to recast into a hollow cylinder of external diameter 20 cm, 0.25 cm thick and 15 cm long?

Solution 5

External diameter of hollow cylinder = 20 cm

Therefore, radius = 10 cm

Thickness = 0.25 cm

Hence, internal radius = (10 - 0.25) = 9.75 cm

Length of cylinder (h) = 15 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter = 2 cm

Therefore, radius (r) = 1 cm

Let h be the length

then, Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now, according to given condition:

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Length of cylinder = 74.0625 cm

Question 6

A cylinder has a diameter of 20 cm. The area of curved surface is 100 sq cm. Find:

(i) the height of the cylinder correct to one decimal place.

(ii) the volume of the cylinder correct to one decimal place.

Solution 6

Diameter of the cylinder = 20 cm

Hence, Radius (r) = 10 cm

Height = h cm

(i) Curved surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Volume of the cylinder = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

or

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 7

A metal pipe has a bore (inner diameter) of 5 cm. The pipe is 5 mm thick all round. Find the weight, in kilogram, of 2 metres of the pipe if 1 cm3 of the metal weights 7.7 g.

Solution 7

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 8

A cylindrical container with diameter of base 42 cm contains sufficient water to submerge a rectangular solid of iron with dimensions 22 cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumex 14 cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 10.5 cm. Find the rise in level of the water when the solid is submerged.

Solution 8

Diameter of cylindrical container = 42 cm

Therefore, radius (r) = 21 cm

Dimensions of rectangular solid = 22cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 14cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 10.5cm

Volume of solid = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let height of water = h

Therefore, volume of water in the container = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 9

A cylindrical container with internal radius of its base 10 cm, contains water up to a height of 7 cm. Find the area of wetted surface of the cylinder.

Solution 9

Internal radius of the cylindrical container = 10 cm

Height of water = 7 cm

Therefore, surface area of the wetted surface =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 10

Find the total surface area of an open pipe of length 50 cm, external diameter 20 cm and internal diameter 6 cm.

Solution 10

Length of an open pipe = 50 cm

External diameter = 20 cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume External radius (R) = 10 cm

Internal diameter = 6 cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume Internal radius (r) = 3 cm

Surface area of pipe open from both sides =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area of upper and lower part =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 11

The height and radius of base of a cylinder are in the ratio 3:1. If its volume is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumefind its total surface area.

Solution 11

Ratio between height and radius of a cylinder = 3:1

Volume = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume …….(i)

Let radius of the base = r

then height = 3r

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

from (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, radius = 7 cm and height = 3 x 7 = 21 cm

Now, total surface area =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 12

The radius of a solid right circular cylinder increases by 20% and its height decreases by 20%. Find the percentage change in its volume.

Solution 12

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 13

The radius of a solid right circular cylinder decreases by 20% and its height increases by 10%. Find the percentage change in its :

(i) volume (ii) curved surface area

Solution 13

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 14

Find the minimum length in cm and correct to nearest whole number of the thin metal sheet required to make a hollow and closed cylindrical box of diameter 20 cm and height 35 cm. Given that the width of the metal sheet is 1 m. Also, find the cost of the sheet at the rate of Rs. 56 per m.

Find the area of metal sheet required, if 10% of it is wasted in cutting, overlapping, etc.

Solution 14

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 15

3080 cm3 of water is required to fill a cylindrical vessel completely and 2310 cm3 of water is required to fill it upto 5 cm below the top. Find :

(i) radius of the vessel.

(ii) height of the vessel.

(iii) wetted surface area of the vessel when it is half-filled with water.

Solution 15

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 16

Find the volume of the largest cylinder formed when a rectangular piece of paper 44 cm by 33 cm is rolled along it :

(i) shorter side. (ii) longer side.

Solution 16

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 17

A metal cube of side 11 cm is completely submerged in water contained in a cylindrical vessel with diameter 28 cm. Find the rise in the level of water.

Solution 17

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 18

A circular tank of diameter 2 m is dug and the earth removed is spread uniformly all around the tank to form an embankment 2 m in width and 1.6 m in height. Find the depth of the circular tank.

Solution 18

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 19

The sum of the inner and the outer curved surfaces of a hollow metallic cylinder is 1056 cm2 and the volume of material in it is 1056 cm3. Find its internal and external radii. Given that the height of the cylinder is 21 cm.

Solution 19

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 20

The difference between the outer curved surface area and the inner curved surface area of a hollow cylinder is 352 cm2. If its height is 28 cm and the volume of material in it is 704 cm3;find its external curved surface area.

Solution 20

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 21

The sum of the heights and the radius of a solid cylinder is 35 cm and its total surface area is 3080 cm2, find the volume of the cylinder.

Solution 21

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 22

The total surface area of a solid cylinder is 616 cm2. If the ratio between its curved surface area and total surface area is 1 : 2; find the volume of the cylinder.

Solution 22

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 23

A cylindrical vessel of height 24 cm and diameter 40 cm is full of water. Find the exact number of small cylindrical bottles, each of height 10 cm and diameter 8 cm, which can be filled with this water.

Solution 23

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 24

Two solid cylinders, one with diameter 60 cm and height 30 cm and the other with radius 30 cm and height 60 cm, are metled and recasted into a third solid cylinder of height 10 cm. Find the diameter of the cylinder formed.

Solution 24

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 25

The total surface area of a hollow cylinder, which is open from both sides, is 3575 cm2; area of the base ring is 357.5 cm2 and height is 14 cm. Find the thickness of the cylinder.

Solution 25

Total surface area of a hollow cylinder = 3575 cm2

Area of the base ring = 357.5 cm2

Height = 14 cm

Let external radius = R and internal radius = r

Let thickness of the cylinder = d = (R-r)

Therefore, Total surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

and Area of base =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Dividing (i) by (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, thickness of the cylinder = 3.5 cm

Question 26

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 

 

The given figure shows a solid formed of a solid cube of side 40cm and a solid cylinder of radius 20 cm and height 50 cm attached to the cube as shown.

Find the volume and the total surface area of the whole solid (Take π = 3.14)

Solution 26

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 27

Two right circular solid cylinders have radii in the ratio 3 : 5 and heights in the ratio 2 : 3, Find the ratio between their :

(i) curved surface areas.

(ii) volumes.

Solution 27

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 28

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 28

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume) Exercise Ex. 20(B)

Question 1

Find the volume of a cone whose slant height is 17 cm and radius of base is 8 cm.

Solution 1

Slant height (Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume) = 17 cm

Radius (r) = 8 cm

But,

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now, volume of cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 2

The curved surface area of a cone is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume If the radius of its base is 56 cm, find its height.

Solution 2

Curved surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of base (r) = 56 cm

Let slant height = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of the cone =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 3

The circumference of the base of a 12 m high conical tent is 66 m. Find the volume of the air contained in it.

Solution 3

Circumference of the conical tent = 66 m

and height (h) = 12 m

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, volume of air contained in it = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 4

The radius and height of a right circular cone are in the ratio 5:12 and its volume is 2512 cubic cm. Find the radius and slant height of the cone. (Take Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 4

The ratio between radius and height = 5:12

Volume = 5212 cubic cm

Let radius (r) = 5x, height (h) = 12x and slant height = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now Volume = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 5

Two right circular cones x and y are made, x having three times the radius of y and y having half the volume of x. Calculate the ratio between the heights of x and y.

Solution 5

Let radius of cone y = r

Therefore, radius of cone x = 3r

Let volume of cone y = V

then volume of cone x = 2V

Let h1 be the height of x and h2 be the height of y.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, Volume of cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of cone x = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of cone y = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 6

The diameters of two cones are equal. If their slant heights are in the ratio 5:4, find the ratio of their curved surface areas.

Solution 6

Let radius of each cone = r

Ratio between their slant heights = 5:4

Let slant height of the first cone = 5x

and slant height of second cone = 4x

Therefore, curved surface area of the first cone =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

curved surface area of the second cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, ratio between them = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 7

There are two cones. The curved surface area of one is twice that of the other. The slant height of the latter is twice that of the former. Find the ratio of their radii.

Solution 7

Let slant height of the first cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

then slant height of the second cone = 2Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of the first cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of the second cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Then, curved surface area of first cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

curved surface area of second cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

According to given condition:

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 8

A heap of wheat is in the form of a cone of diameter 16.8 m and height 3.5 m. Find its volume. How much cloth is required to just cover the heap?

Solution 8

Diameter of the cone = 16.8 m

Therefore, radius (r) = 8.4 m

Height (h) = 3.5 m

(i) Volume of heap of wheat = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Slant height (Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume) = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, cloth required or curved surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 9

Find what length of canvas, 1.5 m in width, is required to make a conical tent 48 m in diameter and 7 m in height. Given that 10% of the canvas is used in folds and stitching. Also, find the cost of the canvas at the rate of Rs. 24 per meter.

Solution 9

Diameter of the tent = 48 m

Therefore, radius (r) = 24 m

Height (h) = 7 m

Slant height (Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume) = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Curved surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Canvas required for stitching and folding

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total canvas required (area)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Length of canvas

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Rate = Rs 24 per meter

Total cost Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 10

A solid cone of height 8 cm and base radius 6 cm is melted and re-casted into identical cones, each of height 2 cm and diameter 1 cm. Find the number of cones formed.

Solution 10

Height of solid cone (h) = 8 cm

Radius (r) = 6 cm

Volume of solid cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of smaller cone = 2 cm

and radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of smaller cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Number of cones so formed

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 11

The total surface area of a right circular cone of slant height 13 cm is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume. Calculate:

(i) its radius in cm

(ii) its volume in cm3. Take Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 11

Total surface area of cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

slant height (l) = 13 cm

(i) Let r be its radius, then

Total surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Either r+18 = 0, then r = -18 which is not possible

or r-5=0, then r = 5

Therefore, radius = 5 cm

(ii) Now

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 12

The area of the base of a conical solid is 38.5 cm2 and its volume is 154 cm3. Find the curved surface area of the solid.

Solution 12

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 13

A vessel, in the form of an inverted cone, is filled with water to the brim. Its height is 32 cm and diameter of the base is 25.2 cm. Six equal solid cones are dropped in it, so that they are fully submerged. As a result, one-fourth of water in the original cone overflows. What is the volume of each of the solid cones submerged?

Solution 13

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of vessel = volume of water = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

diameter = 25.2 cm, therefore radius = 12.6 cm

height = 32 cm

Volume of water in the vessel = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

On submerging six equal solid cones into it, one-fourth of the water overflows.

Therefore, volume of the equal solid cones submerged

= Volume of water that overflows

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now, volume of each cone submerged

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 14

The volume of a conical tent is 1232 m3 and the area of the base floor is 154 m2. Calculate the:

(i) radius of the floor

(ii) height of the tent

(iii) length of the canvas required to cover this conical tent if its width is 2 m.

Solution 14

(i) Let r be the radius of the base of the conical tent, then area of the base floor = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, radius of the base of the conical tent i.e. the floor = 7 m

(ii) Let h be the height of the conical tent, then the volume =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, the height of the tent = 24 m

(iii) Let l be the slant height of the conical tent, then Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

The area of the canvas required to make the tent = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Length of the canvas required to cover the conical tent of its width 2 m = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume) Exercise Ex. 20(C)

Question 1

The surface area of a sphere is 2464 cm2, find its volume.

Solution 1

Surface area of the sphere = 2464 cm2

Let radius = r, then

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 2

The volume of a sphere is 38808 cm3; find its diameter and the surface area.

Solution 2

Volume of the sphere = 38808 cm3

Let radius of sphere = r

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 3

A spherical ball of lead has been melted and made into identical smaller balls with radius equal to half the radius of the original one. How many such balls can be made?

Solution 3

Let the radius of spherical ball = r

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of smaller ball = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, number of smaller balls made out of the given ball =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 4

How many balls each of radius 1 cm can be made by melting a bigger ball whose diameter is 8 cm.

Solution 4

Diameter of bigger ball = 8 cm

Therefore, Radius of bigger ball = 4 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of small ball = 1 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Number of balls = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 5

8 metallic sphere; each of radius 2 mm, are melted and cast into a single sphere. Calculate the radius of the new sphere.

Solution 5

Radius of metallic sphere = 2 mm = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of 8 spheres = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let radius of new sphere = R

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 6

The volume of one sphere is 27 times that of another sphere. Calculate the ratio of their:

(i) radii

(ii) surface areas

Solution 6

Volume of first sphere = 27 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume volume of second sphere

Let radius of first sphere =Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

and radius of second sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, volume of first sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

and volume of second sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(i) Now, according to the question

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Surface area of first sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

and surface area of second sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Ratio in surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 7

If the number of square centimeters on the surface of a sphere is equal to the number of cubic centimeters in the volume, what is the diameter of the sphere?

Solution 7

Let r be the radius of the sphere.

Surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume and volume = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

According to the condition:

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of sphere = 2 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 3 cm = 6 cm

Question 8

A solid metal sphere is cut through its centre into 2 equal parts. If the diameter of the sphere is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumefind the total surface area of each part correct to 2 decimal places.

Solution 8

Diameter of sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, radius of sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total curved surface area of each hemispheres =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 9

The internal and external diameters of a hollow hemi-spherical vessel are 21 cm and 28 cm respectively. Find:

(i) internal curved surface area

(ii) external curved surface area

(iii) total surface area

(iv) volume of material of the vessel.

Solution 9

External radius (R) = 14 cm

Internal radius (r) = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(i) Internal curved surface area =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) External curved surface area =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(iii) Total surface area =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(iv) Volume of material used =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 10

A solid sphere and a solid hemi-sphere have the same total surface area. Find the ratio between their volumes.

Solution 10

Let the radius of the sphere be 'r1'.

Let the radius of the hemisphere be 'r2'

TSA of sphere = 4∏r12

TSA of hemisphere = 3∏r22

TSA of sphere = TSA of hemi-sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 

Volume of sphere, V1 = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of hemisphere, V2 = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 

 

Dividing V1 by V2,

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Question 11

Metallic spheres of radii 6 cm, 8 cm and 10 cm respectively are melted and recasted into a single solid sphere. Taking ∏ = 3.1, find the surface area of solid sphere formed.

Solution 11

Let radius of the larger sphere be 'R'

Volume of single sphere

= Vol. of sphere 1 + Vol. of sphere 2 + Vol. of sphere 3

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Surface area of the sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

Question 12

The surface area of a solid sphere is increased by 21% without changing its shape. Find the percentage increase in its:

(i) radius

(ii) volume

Solution 12

Let the radius of the sphere be 'r'.

Total surface area the sphere, S Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 

New surface area of the sphere, S'

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

(i) Let the new radius be r1

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Percentage change in radius


Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume


Percentage change in radius = 10%


(ii) Let the volume of the sphere be V

Let the new volume of the sphere be V'.


Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Percentage change in volume =33.1%

Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume) Exercise Ex. 20(D)

Question 1

A solid sphere of radius 15 cm is melted and recast into solid right circular cones of radius 2.5 cm and height 8 cm. Calculate the number of cones recast.

Solution 1

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 2

A hollow sphere of internal and external diameters 4 cm and 8 cm respectively is melted into a cone of base diameter 8 cm. Find the height of the cone.

Solution 2

External diameter = 8 cm

Therefore, radius (R) = 4 cm

Internal diameter = 4 cm

Therefore, radius (r) = 2 cm

Volume of metal used in hollow sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of cone = 8 cm

Therefore, radius = 4 cm

Let height of cone = h

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of the cone = 14 cm

Question 3

The radii of the internal and external surfaces of a metallic spherical shell are 3 cm and 5 cm respectively. It is melted and recast into a solid right circular cone of height 32 cm. find the diameter of the base of the cone.

Solution 3

Internal radius = 3cm

External radius = 5 cm

Volume of spherical shell

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Volume of solid circular cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Vol. of Cone = Vol. of sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume


Hence, diameter = 2r = 7 cm

 

 

Question 4

Total volume of three identical cones is the same as that of a bigger cone whose height is 9 cm and diameter 40 cm. find the radius of the base of each smaller cone, if height of each is 108 cm.

Solution 4

Let the radius of the smaller cone be 'r' cm.

Volume of larger cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Volume of smaller cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Volume of larger cone=3× Volume of smaller cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

Question 5

A solid rectangular block of metal 49 cm by 44 cm by 18 cm is melted and formed into a solid sphere. Calculate the radius of the sphere.

Solution 5

Volume of rectangular block = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let r be the radius of sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of sphere = 21 cm

Question 6

A hemi-spherical bowl of internal radius 9 cm is full of liquid. This liquid is to be filled into conical shaped small containers each of diameter 3 cm and height 4 cm. How many containers are necessary to empty the bowl?

Solution 6

Radius of hemispherical bowl = 9 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter each of cylindrical bottle = 3 cm

Radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumecm, and height = 4 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 7

A hemispherical bowl of diameter 7.2 cm is filled completely with chocolate sauce. This sauce is poured into an inverted cone of radius 4.8 cm. Find the height of the cone if it is completely filled.

Solution 7

Diameter of the hemispherical bowl = 7.2 cm

Therefore, radius = 3.6 cm

Volume of sauce in hemispherical bowl = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of the cone = 4.8 cm

Volume of cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now, volume of sauce in hemispherical bowl = volume of cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of the cone = 4.05 cm

Question 8

A solid cone of radius 5 cm and height 8 cm is melted and made into small spheres of radius 0.5 cm. Find the number of spheres formed.

Solution 8

Radius of a solid cone (r) = 5 cm

Height of the cone = 8 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And VolumeVolume of a cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 9

The total area of a solid metallic sphere is 1256 cm2. It is melted and recast into solid right circular cones of radius 2.5 cm and height 8 cm. Calculate:

(i) the radius of the solid sphere

(ii) the number of cones recasted [Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume]

Solution 9

Total area of solid metallic sphere = 1256 cm2

(i)Let radius of the sphere is r then

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Volume of sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And VolumeVolume of right circular cone =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Number of cones

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 10

A solid metallic cone, with radius 6 cm and height 10 cm, is made of some heavy metal A. In order to reduce weight, a conical hole is made in the cone as shown and it is completely filled with a lighter  metal B. The conical hole has a diameter of 6 cm and depth 4 cm. Calculate the ratio of the volume of the metal A to the volume of metal B in the solid.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 10

Volume of the whole cone of metal A

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Volume of the cone with metal B

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

Final Volume of cone with metal A=120 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume-12 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume=108 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

 

 

Question 11

A hollow sphere of internal and external radii 6 cm and 8 cm respectively is melted and recast into small cones of base radius 2 cm and height 8 cm. Find the number of cones.

Solution 11

Let the number of small cones be 'n'

Volume of sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

Volume of small spheres

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Volume of sphere = n× Volume of small sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

The number of cones = 37

Question 12

The surface area of a solid metallic sphere is 2464 cm2. It is melted and recast into solid right circular cones of radius 3.5 cm and height 7 cm. Calculate :

(i) the radius of the sphere.

(ii) the number of cones recast. Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 12

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume) Exercise Ex. 20(E)

Question 1

A cone of height 15 cm and diameter 7 cm is mounted on a hemisphere of same diameter. Determine the volume of the solid thus formed.

Solution 1

Height of cone = 15 cm

and radius of the base = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumecm

Therefore, volume of the solid = volume of the conical part + volume of hemispherical part.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 2

A buoy is made in the form of a hemisphere surmounted by a right cone whose circular base coincides with the plane surface of the hemisphere. The radius of the base of the cone is 3.5 m and its volume is two-third of the hemisphere. Calculate the height of the cone and the surface area of the buoy, correct to two decimal places.

Solution 2

Radius of hemispherical part (r) = 3.5 m = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, Volume of hemisphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of conical part = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume (2/3 of hemisphere)

Let height of the cone = h

Then,

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of the cone = 4.67 m

Surface area of buoy = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

But Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, Surface area =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Surface Area = 141.17 m2

Question 3

From a rectangular solid of metal 42 cm by 30 cm by 20 cm, a conical cavity of diameter 14 cm and depth 24 cm is drilled out. Find:

(i) the surface area of the remaining solid

(ii)the volume of remaining solid

(iii) the weight of the material drilled out if it weighs 7 gm per cm3.

Solution 3

(i) Total surface area of cuboid = 2(Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumeb + bh + Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumeh)

=2(42 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 30 + 30 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume20 + 20 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume42)

=2(1260 + 600 + 840)

=2 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 2700

=5400 cm2

Diameter of the cone = 14 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And VolumeRadius of the cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area of circular baseSelina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area of curved surface area of coneSelina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Surface area of remaining part Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Dimensions of rectangular solids = (42 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 30 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 20) cm

volume = (42 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 30 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 20) = 25200 cm3

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of conical cavity (r) =7 cm

height (h) = 24 cm

Volume of cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of remaining solid = (25200 - 1232) = 23968 cm3

(iii) Weight of material drilled out

=1232 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 7 g = 8624g = 8.624 kg

Question 4

The cubical block of side 7 cm is surmounted by a hemisphere of the largest size. Find the surface area of the resulting solid.

Solution 4

The diameter of the largest hemisphere that can be placed on a face of a cube of side 7 cm will be 7 cm.

Therefore, radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Its curved surface area =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Surface area of the top of the resulting solid = Surface area of the top face of the cube - Area of the base of the hemisphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Surface area of the cube = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total area of resulting solid = 245 + 10.5 + 77 = 332.5 cm2

Question 5

A vessel is in the form of an inverted cone. Its height is 8 cm and the radius of the top which is open is 5 cm. It is filled with water up to the rim. When lead shots, each of which is a sphere of radius 0.5 cm, are dropped into the vessel, one-fourth of the water flows out. Find the number of lead shots dropped in the vessel.

Solution 5

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of cone = 8 cm

Radius = 5 cm

Volume = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, volume of water that flowed out =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Radius of each ball = 0.5 cm = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of a ball = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, No. of balls = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, number of lead balls = 100

Question 6

A hemispherical bowl has negligible thickness and the length of its circumference is 198 cm. find the capacity of the bowl.

Solution 6

Let r be the radius of the bowl.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Capacity of the bowl =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 7

Find the maximum volume of a cone that can be carved out of a solid hemisphere of radius r cm.

Solution 7

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

For the volume of cone to be largest, h = r cm

Volume of the cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 


Question 8

The radii of the bases of two solid right circular cones of same height are r1 and r2 respectively. The cones are melted and recast into a solid sphere of radius R. Find the height of each cone in terms r1, r2 and R.

Solution 8

Let the height of the solid cones be 'h'

Volume of solid circular cones

  Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of sphere = Volume of cone 1 + volume of cone 2


Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume


Question 9

A solid metallic hemisphere of diameter 28 cm is melted and recast into a number of identical solid cones, each of diameter 14 cm and height 8 cm. Find the number of cones so formed.

Solution 9

Volume of the solid hemisphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Volume of 1 cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume


No. of cones formed


Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 


Question 10

A cone and a hemisphere have the same base and same height. Find the ratio between their volumes.

Solution 10

Let the radius of base be 'r' and the height be 'h'

Volume of cone, Vc

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Volume of hemisphere, Vh

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume) Exercise Ex. 20(F)

Question 1

From a solid right circular cylinder with height 10 cm and radius of the base 6 cm, a right circular cone of the same height and same base are removed. Find the volume of the remaining solid.

Solution 1

Height of the cylinder (h) = 10 cm

and radius of the base (r) = 6 cm

Volume of the cylinder = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of the cone = 10 cm

Radius of the base of cone = 6 cm

Volume of the cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of the remaining part

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 2

From a solid cylinder whose height is 16 cm and radius is 12 cm, a conical cavity of height 8 cm and of base radius 6 cm is hollowed out. Find the volume and total surface area of the remaining solid.

Solution 2

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of solid cylinder (R) = 12 cm

and Height (H) = 16 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of cone (r) = 6 cm, and height (h) = 8 cm.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(i) Volume of remaining solid

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Slant height of cone Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, total surface area of remaining solid = curved surface area of cylinder + curved surface area of cone + base area of cylinder + area of circular ring on upper side of cylinder

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 3

A circus tent is cylindrical to a height of 4 m and conical above it. If its diameter is 105 m and its slant height is 80 m, calculate the total area of canvas required. Also, find the total cost of canvas used at Rs 15 per meter if the width is 1.5 m

Solution 3

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of the cylindrical part of the tent (r) = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Slant height (Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume) = 80 m

Therefore, total curved surface area of the tent = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Width of canvas used = 1.5 m

Length of canvas = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total cost of canvas at the rate of Rs 15 per meter

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 4

A circus tent is cylindrical to a height of 8 m surmounted by a conical part. If total height of the tent is 13 m and the diameter of its base is 24 m; calculate:

(i) total surface area of the tent

(ii) area of canvas, required to make this tent allowing 10% of the canvas used for folds and stitching.

Solution 4

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of the cylindrical part = H = 8 m

Height of the conical part = h = (13-8)m = 5 m

Diameter = 24 m Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume radius = r = 12 m

 

Slant height of the cone = l

 

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Slant height of cone = 13 m

 

(i) Total surface area of the tent = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii)Area of canvas used in stitching = total area

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 5

A cylindrical boiler, 2 m high, is 3.5 m in diameter. It has a hemispherical lid. Find the volume of its interior, including the part covered by the lid.

Solution 5

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of cylindrical boiler = 3.5 m

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height (h) = 2 m

Radius of hemisphere (R) = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total volume of the boiler = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 6

A vessel is a hollow cylinder fitted with a hemispherical bottom of the same base. The depth of the cylindrical part is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume and the diameter of hemisphere is 3.5 m. Calculate the capacity and the internal surface area of the vessel.

Solution 6

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of the base = 3.5 m

Therefore, radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of cylindrical part = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(i) Capacity (volume) of the vessel = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii)Internal curved surface area = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 7

A wooden toy is in the shape of a cone mounted on a cylinder as shown alongside.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

If the height of the cone is 24 cm, the total height of the toy is 60 cm and the radius of the base of the cone = twice the radius of the base of the cylinder = 10 cm; find the total surface area of the toy. [Take Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume]

Solution 7

Height of the cone = 24 cm

Height of the cylinder = 36 cm

Radius of the cone = twice the radius of the cylinder = 10 cm

Radius of the cylinder = 5 cm

Slant height of the cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now, the surface area of the toy = curved area of the conical point + curved area of the cylinder

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 8

A cylindrical container with diameter of base 42 cm contains sufficient water to submerge a rectangular solid of iron with dimensions 22 cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume14 cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 10.5 cm. Find the rise in level of the water when the solid is submerged.

Solution 8

Diameter of cylindrical container = 42 cm

Therefore, radius (r) = 21 cm

Dimensions of rectangular solid = 22cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 14cm Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 10.5cm

Volume of solid = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let height of water = h

Therefore, volume of water in the container = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 9

Spherical marbles of diameter 1.4 cm are dropped into beaker containing some water and are fully submerged. The diameter of the beaker is 7 cm. Find how many marbles have been dropped in it if the water rises by 5.6 cm.

Solution 9

Diameter of spherical marble = 1.4 cm

Therefore, radius = 0.7 cm

Volume of one ball Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of beaker = 7 cm

Therefore, radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of water = 5.6 cm

Volume of water = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

No. of balls dropped

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 10

The cross-section of a railway tunnel is a rectangle 6 m broad and 8 m high surmounted by a semi-circle as shown in the figure.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

The tunnel is 35 m long. Find the cost of plastering the internal surface of the tunnel (excluding the floor) at the rate of Rs 2.25 per m2.

Solution 10

Breadth of the tunnel = 6 m

Height of the tunnel = 8 m

Length of the tunnel = 35 m

Radius of the semi-circle = 3 m

Circumference of the semi-circle = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Internal surface area of the tunnel

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Rate of plastering the tunnel = Rs 2.25 per m2

Therefore, total expenditure Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 11

The horizontal cross-section of a water tank is in the shape of a rectangle with semicircle at one end, as shown in the following figure.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

The water is 2.4 metres deep in the tank. Calculate the volume of water in the tank in gallons. (Given: 1 gallon = 4.5 litres)

Solution 11

Length = 21 m

Depth of water = 2.4 m

Breadth = 7 m

Therefore, radius of semicircle = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area of cross-section = area of rectangle + Area of semicircle

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, Volume of water filled in gallons

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 12

The given figure shows the cross-section of a water channel consisting of a rectangle and a semicircle. Assuming that the channel is always full, find the volume of water discharged through it in one minute if water is flowing at the rate of 20 cm per second. Give your answer in cubic meters correct to one place of decimal.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 12

Length = 21 cm, Breadth = 7 cm

Radius of semicircle = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area of cross section of the water channel = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Flow of water in one minute at the rate of 20 cm per second

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And VolumeLength of the water column = 20 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 60 = 1200 cm

Therefore, volume of water =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 13

An open cylindrical vessel of internal diameter 7 cm and height 8 cm stands on a horizontal table. Inside this is placed a solid metallic right circular cone, the diameter of whose base is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumecm and height 8 cm. Find the volume of water required to fill the vessel. If this cone is replaced by another cone, whose height is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volumecm and radius of whose base is 2 cm, find the drop in the water level.

Solution 13

Diameter of the base of the cylinder = 7 cm

Therefore, radius of the cylinder = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of the cylinder Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of the base of the cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, radius of the cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of the cone Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

On placing the cone into the cylindrical vessel, the volume of the remaining portion where the water is to be filled

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of new cone = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius = 2 cm

Therefore, volume of new cone

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of water which comes down = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let h be the height of water which is dropped down.

Radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Drop in water level = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 14

A cylindrical can, whose base is horizontal and of radius 3.5 cm, contains sufficient water so that when a sphere is placed in the can, the water just covers the sphere. Given that the sphere just fits into the can, calculate:

(i) the total surface area of the can in contact with water when the sphere is in it;

(ii) the depth of water in the can before the sphere was put into the can.

Solution 14

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of the base of the cylindrical can = 3.5 cm

(i) When the sphere is in can, then total surface area of the can =

Base area + curved surface area

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Let depth of water = x cm

When sphere is not in the can, then volume of the can =

volume of water + volume of sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 15

 A hollow cylinder has solid hemisphere inward at one end and on the other end it is closed with a flat circular plate. The height of water is 10 cm when flat circular surface is downward. Find the level of water, when it is inverted upside down, common diameter is 7 cm and height of the cylinder is 20 cm.

Solution 15

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let the height of the water level be 'h', after the solid is turned upside down.

Volume of water in the cylinder

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Volume of the hemisphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Volume of water in the cylinder

= Volume of water level - Volume of the hemisphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

Chapter 20 - Cylinder, Cone and Sphere (Surface Area and Volume) Exercise Ex. 20(G)

Question 1

What is the least number of solid metallic spheres, each of 6 cm diameter, that should be melted and recast to form a solid metal cone whose height is 45 cm and diameter is 12 cm?

Solution 1

Let the number of solid metallic spheres be 'n'

Volume of 1 sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of metallic cone

= Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

The least number of spheres needed to form the cone is 15

Question 2

A largest sphere is to be carved out of a right circular cylinder of radius 7 cm and height 14 cm. Find the volume of the sphere. (Answer correct to the nearest integer)

Solution 2

Radius of largest sphere that can be formed inside the cylinder should be equal to the radius of the cylinder.

 

 

Radius of the largest sphere = 7 cm

Volume of sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

 

 

 

 

Question 3

A right circular cylinder having diameter 12 cm and height 15 cm is full of ice-cream. The ice-cream is to be filled in identical cones of height 12 cm and diameter 6 cm having a hemi-spherical shape on the top. Find the number of cones required.

Solution 3

Let the number of cones be 'n'.

Volume of the cylinder = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume


Volume of ice-cream cone = Volume of cone + Volume of hemisphere


                                     Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

Hence, number of cones required = 10

Question 4

A solid is in the form of a cone standing on a hemisphere with both their radii being equal to 8 cm and the height of cone is equal to its radius. Find in terms of Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume, the volume of the solid.

Solution 4

 Volume of the solid

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

 

 

 

 

 

 

Question 5

The diameter of a sphere is 6 cm. It is melted and drawn into a wire of diameter 0.2 cm. Find the length of wire.

Solution 5

Diameter of a sphere = 6 cm

Radius = 3 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of cylindrical wire = 0.2 cm

Therefore, radius of wire = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let length of wire = h

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, length of the wire = 36 m

Question 6

Determine the ratio of the volume of a cube to that of a sphere which will exactly fit inside the cube.

Solution 6

Let edge of the cube = a

volume of the cube = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

The sphere, which exactly fits in the cube, has radius = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, volume of sphere = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of cube : volume of sphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 7

An iron pole consisting of a cylindrical portion 110 cm high and of base diameter 12 cm is surmounted by a cone 9 cm high. Find the mass of the pole, given that 1 cm3 of iron has 8 gm of mass (approx). Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 7

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of the base of poles (r) = 6 cm

Height of the cylindrical part (h1) = 110 cm

Height of the conical part (h2) = 9 cm

Total volume of the iron pole = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Weight of 1 cm3 = 8 gm

Therefore, total weight = 12780 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 8 = 102240 gm = 102.24 kg

Question 8

In the following diagram a rectangular platform with a semicircular end on one side is 22 meters long from one end to the other end. If the length of the half circumference is 11 meters, find the cost of constructing the platform, 1.5 meters high at the rate of Rs 4 per cubic meters.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 8

Length of the platform = 22 m

Circumference of semicircle = 11 m

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, breadth of the rectangular part = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

And length = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now area of platform = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Height of the platform = 1.5 m

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Rate of construction = Rs 4 per m3

Total expenditure = Rs 4 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 223.125 = Rs 892.50

Question 9

The cross-section of a tunnel is a square of side 7 m surmounted by a semicircle as shown in the following figure.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

The tunnel is 80 m long. Calculate:

(i) its volume

(ii) the surface area of the tunnel (excluding the floor) and

(iii) its floor area

Solution 9

Side of square = 7 m

Radius of semicircle = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Length of the tunnel = 80 m

Area of cross section of the front part = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(i) Therefore, volume of the tunnel = area x length

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Circumference of the front of tunnel

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, surface area of the inner part of the tunnel

= 25 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 80

= 2000 m2

(iii) Area of floor = l Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume b = 7 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 80 = 560 m2

Question 10

A cylindrical water tank of diameter 2.8m and height 4.2m is being fed by a pipe of diameter 7 cm through which water flows at the rate of 4m/s. Calculate, in minutes, the time it takes to fill the tank.

Solution 10

Diameter of cylindrical tank = 2.8 m

Therefore, radius = 1.4 m

Height = 4.2 m

Volume of water filled in it = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of pipe = 7 cm

Therefore, radius (r) = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let length of water in the pipe = h1

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

From (i) and (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, time taken at the speed of 4 m per second

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 11

Water flows, at 9 km per hour, through a cylindrical pipe of cross-sectional area 25 cm2. If this water is collected into a rectangular cistern of dimensions 7.5m by 5m by 4 m; calculate the rise in level in the cistern in 1 hour 15 minutes.

Solution 11

Rate of flow of water = 9 km/hr

Water flow in 1 hour 15 minutes

i.e. in Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Area of cross-section = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, volume of waterSelina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Dimensions of water tank = 7.5m Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 5m Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 4m

Area of tank = l Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume b = 7.5 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume 5 = 37.5 m2

Let h be the height of water then,

37.5 Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume h = 28.125

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 12

The given figure shows the cross-section of a cone, a cylinder and a hemisphere all with the same diameter 10 cm and the other dimensions are as shown. Calculate:

(i) the total surface area

(ii) the total volume of the solid

(iii) the density of the material if its total weight is 1.7 kg

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Solution 12

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter = 10 cm

Therefore, radius (r) = 5 cm

Height of the cone (h) = 12 cm

Height of the cylinder = 12 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(i) Total surface area of the solid

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Total volume of the solid

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(iii) Total weight of the solid = 1.7 kg

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 13

A solid, consisting of a right circular cone, standing on a hemisphere, is placed upright, in a right circular cylinder, full of water, and touches the bottom. Find the volume of water left in the cylinder, having given that the radius of the cylinder is 3 cm and its height is 6 cm; the radius of the hemisphere is 2 cm and the height of the cone is 4 cm. Give your answer to the nearest cubic centimeter.

Solution 13

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of cylinder = 3 cm

Height of cylinder = 6 cm

Radius of hemisphere = 2 cm

Height of cone = 4 cm

Volume of water in the cylinder when it is full =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of water displaced = volume of cone + volume of

hemisphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Therefore, volume of water which is left

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 14

A metal container in the form of a cylinder is surmounted by a hemisphere of the same radius. The internal height of the cylinder is 7 m and the internal radius is 3.5 m. Calculate:

(i) the total area of the internal surface, excluding the base;

(ii) the internal volume of the container in m3.

Solution 14

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Radius of the cylinder = 3.5 m

Height = 7 m

(i) Total surface area of container excluding the base = Curved

surface area of the cylinder + area of hemisphere

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

(ii) Volume of the container = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 15

An exhibition tent is in the form of a cylinder surmounted by a cone. The height of the tent above the ground is 85 m and the height of the cylindrical part is 50 m. If the diameter of the base is 168 m, find the quantity of canvas required to make the tent. Allow 20% extra for fold and for stitching. Give your answer to nearest m2.

Solution 15

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total height of the tent = 85 m

Diameter of the base = 168 m

Therefore, radius (r) = 84 m

Height of the cylindrical part = 50 m

Then height of the conical part = (85 - 50) = 35 m

Slant height (l) Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Total surface area of the tent = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Since 20% extra is needed for folds and stitching,

total area of canvas needed

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 16

A test tube consists of a hemisphere and a cylinder of the same radius. The volume of the water required to fill the whole tube is Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume and Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume of water are required to fill the tube to a level which is 4 cm below the top of the tube. Find the radius of the tube and the length of its cylindrical part.

Solution 16

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of water filled in the test tube = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of water filled up to 4 cm = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Let r be the radius and h be the height of test tube.

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

and

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Dividing (i) by (ii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Subtracting (ii) from (i)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Substituting the value of r in (iii)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Hence, Height = 20 cm and radius = 3.5 cm

Question 17

A solid is in the form of a right circular cone mounted on a hemisphere. The diameter of the base of the cone, which exactly coincides with hemisphere, is 7 cm and its height is 8 cm. The solid is placed in a cylindrical vessel of internal radius 7 cm and height 10 cm. How much water, in cm3, will be required to fill the vessel completely?

Solution 17

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Diameter of hemisphere = 7 cm

Diameter of the base of the cone = 7 cm

Therefore, radius (r) = 3.5 cm

Height (h) = 8 cm

Volume of the solid =

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Now, radius of cylindrical vessel (R) = 7 cm

Height (H) = 10 cm

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Volume of water required to fill = 1540 - 192.5 = 1347.5 cm3

Question 18

Two solid spheres of radii 2 cm and 4 cm are melted and recast into a cone of height 8 cm. Find the radius of the cone so formed.

Solution 18

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 19

A certain number of metallic cones, each of radius 2 cm and height 3 cm, are melted and recast into a solid sphere of radius 6 cm. Find the number of cones used.

Solution 19

Let the number of cones melted be n.

Let the radius of sphere be rs = 6 cm

Radius of cone be rc = 2 cm

And, height of the cone be h = 3 cm

Volume of sphere = n (Volume of a metallic cone)

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

Question 20

A conical tent is to accommodate 77 persons. Each person must have 16m3 of air to breathe. Given the radius of the tent as 7m, find the height of the tent and also its curved surface area.

Solution 20

According to the condition in the question,

Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume

We know that,

l2 = r2 + h2

l2 = (7)2 + (24)2

l2 = 49 + 576

l2 = 625

l = 25 m

Curved Surface Area = πrl = Selina Solutions Icse Class 10 Mathematics Chapter - Cylinder Cone And Sphere Surface Area And Volume× 7× 25 = 550m2

Therefore the height of the tent is 24m and it curved surface area is 550m2. 

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