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.

**Solution:**

Slant height of a frustum of a cone **cm**

Perimeter of its first circular end **cm**

Perimeter of its second circular end **cm**

**Curved Surface Area of frustum of the cone**