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    Question

    If the radius of the base of a right circular cylinder

    is increased by 20% and the height is decreased by 30%, then what is the percentage increase/decrease in the volume?
    A Decrease 0.8% Correct Answer Incorrect Answer
    B Increase 2% Correct Answer Incorrect Answer
    C Increase 0.8% Correct Answer Incorrect Answer
    D Decrease 2% Correct Answer Incorrect Answer

    Solution

    Let the initial radius, height be r, h ⇒ New radius = r + r/5 = 6r/5 ⇒ New height = h – 3h/10 = 7h/10 ⇒ New Area = π × 36r^2/25 × 7h/10 = 252πr^2h/250 ∴% increase in Area = 2/250 x 100 = 0.8%

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