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    Question

    In a class, the ratio of number of boys to number of

    girls is 15:11. If 3 boys joined the class and 1 girl left the class, then the ratio becomes 7:5. Find the actual number of girls in the class.
    A 99 Correct Answer Incorrect Answer
    B 110 Correct Answer Incorrect Answer
    C 121 Correct Answer Incorrect Answer
    D 132 Correct Answer Incorrect Answer
    E 143 Correct Answer Incorrect Answer

    Solution

    Let initially the number of boys and girls be 15x and 11x, respectively.
    (15x + 3) : (11x − 1) = 7 : 5
    Or, 5(15x + 3) = 7(11x − 1)
    Or, 75x + 15 = 77x − 7
    Or, 2x = 22 ⇒ x = 11
    Therefore, number of girls = 11 × 11 = 121 

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