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    Question

    In a school with 400 students, the average of the age of

    the boys is 16 years and that of the girls is 12 years. If the average age of the school is 14 years 9 months. Then the number of girls in the school is.
    A 275 Correct Answer Incorrect Answer
    B 175 Correct Answer Incorrect Answer
    C 137 Correct Answer Incorrect Answer
    D 125 Correct Answer Incorrect Answer

    Solution

    Let the number of Boys be ‘x’ Sum of ages of boys = x x 16 Sum of ages of girls = (400 - x ) x 12 According to question, x × 16 + (400 - x) × 12 = 400 × `14 (3/4)` 16x + 4800 - 12x = 400 × `59/4` 4x + 4800 = 5900 4x = 1100 x = 275 Number of girls = 400 - 275 = 125

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