A container is in the form of a frustum of a cone of height 30 cm with radii of its lower and upper ends as 10 cm and 20 cm respectively.Find the capacity and surface area of the container. Also, find the cost of the milk which can completely fill the container, at the rate of Rs 25 per litre (use = 3.14).

Asked by Topperlearning User | 21st Feb, 2014, 09:46: AM

Expert Answer:

Capacity (or volume) of the container = [r21 + r22 + r1r2]

Here, h = 30 cm, r1 = 20 cm and r2 = 10 cm

So, the capacity of container = 3.14 x[202 + 102 + 20 x 10] cm3

= 21.980 liters

Cost of 1 litre of milk = Rs. 25

Cost of 21.980 litres of milk = Rs. 21.980 x 25 = Rs. 549.50

Surface area of the bucket = curved surface area of the bucket + surface area of the bottom

= l(r1 + r2) +r22

Now, l=

l =cm = 31.62 cm

Therefore, surface area of the bucket

= 3.14 x 31.62 (20 + 10) + 3.14 x (10)2

= 3.14 x 1048.6 cm2 = 3292.6 cm2 (approx.)

Answered by  | 21st Feb, 2014, 11:46: AM

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