Question

A container open at the top, is in the form of a frustum of a cone of height 24 cm with radii of its lower and upper circular ends, as 8 cm and 20 cm respectively. Find the cost of milk which can completely fill the container. at the rate of 21 per litre. [use π=22/7]

Answer 1

Solution:
Volume of a frustum of a cone `=1/3 pih(r1^2+r2^2+r1xxr2)`

Volume of container `=1/3 pih(R^2+r2^2+Rr)`

`=1/3 xx 22/7 xx 24[20xx 20 + 8 xx 8 + 20 xx 8 ]`

`= 15689.14 cm^3`

`= 15.69 litre`

The cost of milk which can completely fill the container at the rate of Rs.21 per liter =Rs(21 x 15.69) = 329.49