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    Question

    The average weight of certain number of students in a

    class is 72 kg. 8 students whose average weight is 75 kg left the class and 3 students whose average weight is 90 kg join the class, because of which the average weight of the class increases by 0.75 kg. Find the total number of students in the class initially.
    A 50 Correct Answer Incorrect Answer
    B 40 Correct Answer Incorrect Answer
    C 45 Correct Answer Incorrect Answer
    D 35 Correct Answer Incorrect Answer

    Solution

    Let, the total number of students in the class initially be 'x'.

    Total weight of the class initially = 72 X x = '72x' kg

    New total weight of the class = 72x - 8 X 75 + 3 X 90 = 72x - 600 + 270 = 72x - 330 kg

    ATQ,

    [(72x - 330) /(x - 5) ] = 72 + 0.75 = 72.75

    Or, 72x - 330 = 72.75 X (x - 5)

    Or, 72x - 330 = 72.75x - 363.75

    Or, 0.75x = 33.75

    Or, x = 45

    So, the number of students in the class initially were 45.

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