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    Question

    X and Y together complete a job in 18 days, while Y

    alone can do it in 30 days. The ratio of efficiencies of X and Z is 4:5 respectively. What is the ratio of efficiencies of Y and Z?
    A 8:9 Correct Answer Incorrect Answer
    B 6:5 Correct Answer Incorrect Answer
    C 5:4 Correct Answer Incorrect Answer
    D 9:10 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let total work = 90 units {LCM of 18 and 30}

    Efficiency of (X + Y) = 90/18 = 5 units/day

    Efficiency of Y = 90/30 = 3 units/day

    Therefore, efficiency of X = 5 – 3 = 2 units/day

    Efficiency of Z = 2 × (5/4) = 2.5 units/day

    Required ratio = 3 : 2.5 = 6 : 5

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