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    Question

    At the rate of a compound interest rate of 4 years, the

    basic amount is tripled in 4 years, in how many years will this original amount be 27 times?
    A 13 Correct Answer Incorrect Answer
    B 14 Correct Answer Incorrect Answer
    C 11 Correct Answer Incorrect Answer
    D 12 Correct Answer Incorrect Answer

    Solution

    The sum triples in 4 years. If it becomes 9 times itself, it has tripled twice. This takes 8 years. Let the sum of P, triple in 4 years at R% per annum. P (1 + R/100)4 = 3P (1 + R/100)4 = 3                … (1) Let it take K years to become 9 times. P (1 + R/100) k = 27P 9 = (1 + R/100) k [(1 + R/100)4] k/4 = 33 3k/4 = 33, K/4 = 3 K = 12 The required result will be 12. Smart Approach- In 4 years =3 times In K year =27 =33 K =4×3 =12 years.

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