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    Question

    Rohit invested a sum on compound interest at 'R%' per

    annum (compounded annually), which amounts to ₹8,000 and ₹11,520 in 2 years and 4 years respectively. Find the value of 'R'.
    A 40 Correct Answer Incorrect Answer
    B 10 Correct Answer Incorrect Answer
    C 20 Correct Answer Incorrect Answer
    D 25 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    So, Principal × [1 + (rate/100)]⁴ = 11,520 ---- (I)
    And, Principal × [1 + (rate/100)]² = 8,000 ---- (II)
    On dividing equation I and II,
    We get, [1 + (rate/100)]² = (11,520 ÷ 8,000)
    Or, [1 + (rate/100)]² = 1.44
    Or, [1 + (rate/100)]² = (1.2)²
    Or, 1 + (rate/100) = 1.2
    Or, (rate/100) = 0.2
    Or, rate = 20%
    So, 'R' = 20

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