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    Question

    The average Economics marks of two sections A and B of

    class X in the annual examination is 70. The average marks of Section A is 72.5 and that of section B is 68. The ratio of the number of students of section A and B is
    A 4:5 Correct Answer Incorrect Answer
    B 6:5 Correct Answer Incorrect Answer
    C 7:8 Correct Answer Incorrect Answer
    D 8:9 Correct Answer Incorrect Answer
    E 10:7 Correct Answer Incorrect Answer

    Solution

    Let the number of students in section A is x and B is y, then   70 =  (72.5 × x + 68 × y)/ (x + y)   ⇒ 70x + 70y = 72.5x + 68y   ⇒  2y = 2.5x      ⇒ x/y = 2/2.5    ⇒ x/y = 4 : 5

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