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    Question

    Rs. 10,200 is the amount after 2 years when invested at r%

    p.a. in simple interest. If the rate had been (r + 6)% p.a., the final amount would be Rs. 10,920. What was the original principal?
    A Rs.6000 Correct Answer Incorrect Answer
    B Rs.5720 Correct Answer Incorrect Answer
    C Rs.6620 Correct Answer Incorrect Answer
    D Rs.4700 Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the sum invested be Rs. ‘P’.

    Simple interest at r% = 10200 – P

    So, 10200 – P = P × 2 × r ÷ 100

    Or, 50 × (10200 – P) = Pr ………. (I)

    Interest at (r + 6)% = 10920 – P

    So, 10920 – P = P × (r + 6) × 2 ÷ 100

    Or, 50 × (10920 – P) = Pr + 6P ………. (II)

    Using (I) and (II),

    546000 – 50P = 510000 – 44P

    36000 = 6P

    P = 6000

    Sum invested = Rs. 6,000

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