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    Question

    ‘M’ and ‘N’ together can do a work in 20 days.

    If ‘M’ increases his efficiency by 25% while ‘N’ decreases his efficiency by 50%, then the time taken to complete the work remains unchanged. Find the ratio of efficiencies of ‘M’ and ‘N’, respectively.
    A 1:2 Correct Answer Incorrect Answer
    B 2:1 Correct Answer Incorrect Answer
    C 3:2 Correct Answer Incorrect Answer
    D 4:3 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the efficiency of ‘M’ and ‘N’ be ‘x’ units/day and ‘y’ units/day, respectively. So, total work = {(x + y) × 20} units After change in efficiencies, Also, total work = (1.25x + 0.5y) × 20 So,
    1.25x + 0.5y = x + y Or,
    0.25x = 0.5y Or,
    x : y = 2 : 1 So, ratio of efficiency of ‘M’ and ‘N’ = 2 : 1

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