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    Question

    If 20 times a number is subtracted from the square of

    the number and then 100 is added to the result, then the result is zero. Find the L.C.M of the number and 15.
    A 60 Correct Answer Incorrect Answer
    B 30 Correct Answer Incorrect Answer
    C 45 Correct Answer Incorrect Answer
    D 90 Correct Answer Incorrect Answer

    Solution

    Let the number be 'x' According to the question, x2 - 20x + 100 = 0 Or, x2 - 10x - 10x + 100 = 0 Or, x(x - 10) - 10(x - 10) = 0 Or, (x - 10)(x - 10) = 0 So, x = 10 L.C.M of 10 and 15 = 30

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