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    Question

    ‘C’ and ‘D’ can complete a piece of work

    together in 24 days. If ‘C’ alone can complete it in 40 days, how long would ‘D’ take to do the same work alone?
    A 50 days Correct Answer Incorrect Answer
    B 26 days Correct Answer Incorrect Answer
    C 60 days Correct Answer Incorrect Answer
    D 20 days Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the total work be 120 units. {LCM (24 and 40)}

    Combined efficiency of 'C' and 'D' = 120 ÷ 24 = 5 units/day

    Efficiency of 'C' = 120 ÷ 40 = 3 units/day

    Efficiency of 'D' = 5 - 3 = 2 units/day

    So, time taken by 'D' alone = 120 ÷ 2 = 60 days

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