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    Question

    In a class of ‘x’ students, if a new student

    weighing 32 kg joins the class, then the average weight of the class increases by 1 kg. If the new student’s weight is 16 kg, then the average weight of the class decreases by 1 kg. Find ‘x’?
    A 6 Correct Answer Incorrect Answer
    B 7 Correct Answer Incorrect Answer
    C 5 Correct Answer Incorrect Answer
    D 8 Correct Answer Incorrect Answer
    E 9 Correct Answer Incorrect Answer

    Solution

    Number of students in the class is x.
    Let the Average weight of the class be y.
    Total weight of the class = xy
    If one student (32 kg) joins, comparing total weight of the class,
    (xy+32)/(x+1) = (y+1)
    x + y = 31 ------- (i)
    If one student (16 kg) joins, comparing total weight of the class,
    (xy + 16)/(x+1) = (y-1)
    -x + y = 17 -------- (ii)
    Solving the equations (i) & (ii) we get,
    x = 7
    Therefore the total number of students in a class is 7.

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