The slant height of a frustum of a cone is 4 cm and the perimeters of its circular ends

Mensuration (10)

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

Answer

Here l = 4 cm, 2πr1 = 18 cm and 2πr2 = 6 cm

πr1= 9, πr2 = 3 

Curved surface area of frustum = π(r1 + r2) × l or (πr1 + πr2) × l 

= (9 + 3) × 4 

= 48 cm2

Exam Year: 2017
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