The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular endsare 18 cm and 6 cm. Find the curved surface area of the frustum
According to the question,
Perimeter of upper circular end of frustum = 18 cm
[2πr1 =18]
r1 = 
Perimeter of lower end of frustum = 6 cm
2πr2 = 6
r2 = 
Slant height (l) of frustum = 4 cm
CSA of frustum = π (r1 + r2) l
= π (
+ 
) * 4
= 12 * 4
= 48 cm2
2