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    Question

    The average age of a class of 20 girls is 12 years. If 4

    new girls having average age of 9 years join the class, then the average age of the class becomes:
    A 9.5 years Correct Answer Incorrect Answer
    B 17 years Correct Answer Incorrect Answer
    C 11.5 years Correct Answer Incorrect Answer
    D 13 years Correct Answer Incorrect Answer

    Solution

    Total age of 20 girls = 20 ×12 = 240 years Total age of 24 girls = 240 + (4×9) = 276 years Therefore new average age = 276/24 = 11.5 years

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