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    Question

    A sum doubles in 20 years at simple interest. What is

    the rate of interest?
    A 5% per annum Correct Answer Incorrect Answer
    B 8% per annum Correct Answer Incorrect Answer
    C 5.5% per annum Correct Answer Incorrect Answer
    D 8.5% per annum Correct Answer Incorrect Answer

    Solution

    Let the original amount = ₹100

    Then after 20 years, it becomes ₹200

    So, interest = ₹100
    SI = (P × R × T)/100


    100 = (100 × R × 20)/100


    100 = 20R/100


    R = 100/20 = 5

    Rate = 5% per year

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