# Class 9 RD SHARMA Solutions Maths Chapter 20 - Surface Areas and Volume of A Right Circular Cone

Ex. 20.1

Ex. 20.2

20.24

20.25

## Surface Areas and Volume of A Right Circular Cone Exercise Ex. 20.1

### Solution 1

### Solution 2

### Solution 3

### Solution 4

### Solution 5

### Solution 6

### Solution 7

### Solution 8

### Solution 9

### Solution 10

### Solution 11

### Solution 12

### Solution 13

### Solution 14

### Solution 15

(i) Slant height of cone = 14 cm

Let radius of circular end of cone be r.

CSA of cone =

Let radius of circular end of cone be r.

CSA of cone =

Thus, the radius of circular end of the cone is 7 cm.

(ii) Total surface area of cone = CSA of cone + Area of base

=

Thus, the total surface area of the cone is 462 .

### Solution 16

### Solution 17

### Solution 18

### Solution 19

Height (h) of conical tent = 8 m

Radius (r) of base of tent = 6 m

Slant height (l) of tent =

CSA of conical tent = = (3.14 6 10) = 188.4

Let length of tarpaulin sheet required be L.

As 20 cm will be wasted so, effective length will be (L - 0.2 m)

Breadth of tarpaulin = 3 m

Area of sheet = CSA of tent

[(L - 0.2 m) 3] m = 188.4

L - 0.2 m = 62.8 m

L = 63 m

Thus, the length of the tarpaulin sheet will be 63 m.

Radius (r) of base of tent = 6 m

Slant height (l) of tent =

CSA of conical tent = = (3.14 6 10) = 188.4

Let length of tarpaulin sheet required be L.

As 20 cm will be wasted so, effective length will be (L - 0.2 m)

Breadth of tarpaulin = 3 m

Area of sheet = CSA of tent

[(L - 0.2 m) 3] m = 188.4

L - 0.2 m = 62.8 m

L = 63 m

Thus, the length of the tarpaulin sheet will be 63 m.

### Solution 20

### Solution 21

### Solution 22

### Solution 23

## Surface Areas and Volume of A Right Circular Cone Exercise Ex. 20.2

### Solution 1

(i) Radius (r) of cone = 6 cm

Height (h) of cone = 7 cm

Volume of cone

(ii) Radius (r) of cone = 3.5 cm

Height (h) of cone = 12 cm

Volume of cone

(iii)

Height (h) of cone = 7 cm

Volume of cone

(ii) Radius (r) of cone = 3.5 cm

Height (h) of cone = 12 cm

Volume of cone

(iii)

### Solution 2

(i) Radius (r) of cone = 7 cm

Slant height (l) of cone = 25 cm

Height (h) of cone

Volume of cone

Capacity of the conical vessel = litres= 1.232 litres

Slant height (l) of cone = 25 cm

Height (h) of cone

Volume of cone

Capacity of the conical vessel = litres= 1.232 litres

(ii) Height (h) of cone = 12 cm

Slant height (l) of cone = 13 cm

Slant height (l) of cone = 13 cm

Radius (r) of cone

Volume of cone = 314.28 cm

^{3}

Capacity of the conical vessel = litres = litres.

### Solution 3

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### Solution 7

### Solution 8

### Solution 9

### Solution 10

### Solution 11

### Solution 12

### Solution 13

(i) Radius of cone = =14 cm

Let height of cone be h.

Volume of cone = 9856 cm

Let height of cone be h.

Volume of cone = 9856 cm

^{3} h = 48 cm

Thus, the height of the cone is 48 cm.

(ii) Slant height (l) of cone

Thus, the slant height of the cone is 50 cm.

(iii) CSA of cone = rl =

### Solution 14

Radius (r) of pit =

Depth (h) of pit = 12 m

Volume of pit =

Depth (h) of pit = 12 m

Volume of pit =

Capacity of the pit = (38.5 1) kilolitres = 38.5 kilolitres

### Solution 15

## Surface Areas and Volume of A Right Circular Cone Exercise 20.24

### Solution 1

A cone has two surfaces as follows: one curved surface and another bottom surface.

Hence, correct option is (b).

### Solution 2

### Solution 3

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### Solution 7

## Surface Areas and Volume of A Right Circular Cone Exercise 20.25

### Solution 8

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### Solution 11

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### Solution 17