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    Question

    The average age of the boys in the class was 16 years.

    When 4 boys whose average age was 13 years are admitted to the class, the average age of the class was reduced by 6 months. How many boys were there initially in the class?
    A 22 Correct Answer Incorrect Answer
    B 20 Correct Answer Incorrect Answer
    C 18 Correct Answer Incorrect Answer
    D 25 Correct Answer Incorrect Answer

    Solution

    The average age of students in a class = 16 years The average age of 4 new students in a class = 13 years Average = Sum of all values/ No. of values. Let the number of students in the class be x. The new average = 16-0.5(6 months) = 15.5 years. (x × 16) + (4 x 13) = (x + 4) x 15.5 16x + 52 = 15.5x + 62.0   0.5x = 10 x = 100/5=20.

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