Question

The lateral surface area of frustum of a right circular cone, if the area of its base is and the diameter of circular upper surface is 4 cm and slant height 6 cm, will be

A 30π cm^2 Correct Answer Incorrect Answer
B 48π cm^2 Correct Answer Incorrect Answer
C 36π cm^2 Correct Answer Incorrect Answer
D 60π cm^2 Correct Answer Incorrect Answer

Solution

r = 4/2 = 2 cm
Also, πR^2 = 16 π
⇒ R^2 = 16
⇒ R = 4
Heightof the frustum h = 6 cm
Lateral surfacea area of the frustum = π (R + r) × l
⇒ π (4 + 2) × 6
⇒ 6 × 6 × π
⇒ 36 π

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