Question

The radii of the circular ends of a frustum of a cone are 20 cm and 13 cm and its height is 12 cm. What is the capacity (in litres) of the frustum (correct to one decimal place)?

(Take `pi = 22/7`)

Options

• 10.4

• 10.8

• 11.2

• 11.4

Answer 1

10.4

Explanation:

Volume of frustum of cone (V) = `1/3 pi (R^2 + r^2 + R.r) xx h`

V = `1/3 xx 22/7 xx (20^2 + 13^2 + 20 xx 13) xx 12`

V = `1/3 xx 22/7 xx 12 xx (400 + 169 + 260)`

V = `1/3 xx 22/7 xx 12 xx 829 = 88 xx 829/7` = 10421.71 cm² = 10.42 litres