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    Question

    An amount becomes five times of itself in 40 years at

    simple interest. Find the value of (3R + 10), where R is the rate of interest per annum.
    A 20 Correct Answer Incorrect Answer
    B 10 Correct Answer Incorrect Answer
    C 40 Correct Answer Incorrect Answer
    D 60 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the amount invested be Rs. 'p'.
    Interest earned = 5p − p = Rs. 4p
    Simple Interest = Principal × Rate × Time ÷ 100
    So, 4p = p × R × 40 ÷ 100
    Or, R = (4 × 100) ÷ 40 = 10
    Required value = 3 × 10 + 10 = 30 + 10 = 40

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