Question

A frustum of a cone is 9 cm thick and the diameters of its circular ends are 28 cm and 4 cm. Find the volume and lateral surface area of the frustum.
(Take π = 22/7).

Answer 1

Volume

`=(pih)/3 (R^2 + Rr + r^2)`

`=9 xx pi /3 ((28/2)^2 + (4/2)^2 + 28/2 xx 4/2)`

`=3pi((14)^2 + 4+14 xx 2)`

`=684 pi cm^3`

S.A. = `pi(14+2)sqrt((14 - 2)^2) + 9 = 240 pi cm^2`