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    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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