Question

    A certain sum of money becomes seven times itself when

    invested at a certain rate of simple interest, in 14 years. How much time (in years, rounded off to 2 decimal places) will it take to become 18 times itself at the same rate?
    A 27.33 Correct Answer Incorrect Answer
    B 39.67 Correct Answer Incorrect Answer
    C 42.78 Correct Answer Incorrect Answer
    D 35.5 Correct Answer Incorrect Answer

    Solution

    Let the principal be P and the rate be R per annum. From the first condition: A =P + SI  7P = P + (P × R × 14)/100 6P = (P × R × 14)/100  R = 600/14 = 42.86  For the second condition: 18P = P + (P × 42.86 × T)/100  17P = (P × 42.86 × T)/100 T = 1700/42.86 ≈ 39.68  The required time is approximately 39.68 years.

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