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    Question

    A certain sum doubles in 9 years at certain rate of simple

    interest. The same sum under the same interest rate will become 4 times of itself in how many years?
    A 15 years Correct Answer Incorrect Answer
    B 27 years Correct Answer Incorrect Answer
    C 36 years Correct Answer Incorrect Answer
    D 18 years Correct Answer Incorrect Answer

    Solution

    Let the sum invested be Rs. ‘x’ and rate of interest be ‘r’ p.a.
    According to the question,
    (x × r × 9)/100 = 2x – x
    Or, r = 100/9
    Therefore, when interest = 4x – x = Rs. 3x, then time will be
    (x × t × 100)/(9 × 100) = 3x
    Or, t = 27 years

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