Question

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

Answer 1

It is given that slant height of frustum of a cone is 4 cm. Circumferences of its ends are

18 cm and 6 cm.

We have to find the curved surface area of the frustum.

Let l be the slant height

Let be the radii of two circular ends of the cone

Circumference of one end

Circumference of other end

Now,

Curved surface area of frustum

(since )