Notifications
Clear all
Surface Areas and Volumes
1
Posts
2
Users
0
Likes
171
Views
0
01/07/2021 1:06 pm
Topic starter
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 surface area of the frustum.
1 Answer
0
01/07/2021 1:07 pm
Slant height (l) = 4 cm
Circumference of upper circular end of the frustum = 18 cm
∴ 2πr1 = 18
r1 = 9/π
Similarly, circumference of lower end of the frustum = 6 cm
∴ 2πr2 = 6
r2 = 6/π
CSA of frustum = π(r1+r2) × l
= π(9/π + 6/π) × 4
= 12 × 4 = 48 cm2