Question

Work out the total surface area of the frustum.

Give your answer to the nearest integer.
32 mm
5 mm
48 mm
15 mm
Not drawn accurately

Answer 1

2639 mm²

Explanation:

Find the SA of the frustum by finding the SA of the full large cone (imagine the top is still there), then subtract the SA of the missing top.

SA = πrl + πr²

l= slant length

Large cone SA = π(15)(48) + π(15²) = 2969

Missing top SA = π(5)(48 - 32) + π(5²) = 330

SA frustum = 2969 - 330 = 2639 mm²