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    Question

    Calculate the curved surface area of a cone with a

    diameter of 42 cm, and a height that is 1 cm shorter than half its diameter.
    A 1,914 cm² Correct Answer Incorrect Answer
    B 1,848 cm² Correct Answer Incorrect Answer
    C 1,892 cm² Correct Answer Incorrect Answer
    D 1,980 cm² Correct Answer Incorrect Answer

    Solution

    Let, the radius, height and slant height of the cone be 'r' cm, 'h' cm, and 'l' cm. r = (42/2) = 21 cm h = 21 - 1 = 20 cm So, l2 = 212 + 202 = 441 + 400 Or, l2 = 841 Since, the slant height cannot be negative. So, l = 29 So, the curved surface area of the cone = π X r X l = (22/7) X 21 X 29 = 1,914 cm2

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