Question

The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the curved surface area of the frustum.

Answer 1

Here, we are given, `l = 4cm`
`2pir_1 = 18cm and 2pir_2 = 6cm`
`pir_1 = 9 and pir_2 = 3`
Now, Curved surface area of frustum, `A = pi(r_1+r_2)l`
`A = (pir_1+pir_2)l = (9+3)**4 = 48cm^2`