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

Perimeter of upper circular end of frustum = 18 cm

2πr₁ =18

Perimeter of lower end of frustum = 6 cm

2πr₂ = 6

Slant height (l) of frustum = 4 cm

CSA of frustum = π (r₁ + r₂) l

Therefore, the curved surface area of the frustum is 48 cm².