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    Question

    ‘X’ and ‘Y’ together can complete a task in 18

    hours. If ‘Y’ alone takes 45 hours to complete the same task, how long will ‘X’ take to do it alone?
    A 1800 mins Correct Answer Incorrect Answer
    B 2100 mins Correct Answer Incorrect Answer
    C 1900 mins Correct Answer Incorrect Answer
    D 3350 mins Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the total work = 90 units {LCM (18 and 45)}

    Efficiency of ‘X’ and ‘Y’ together = (90/18) = 5 units/hour

    Efficiency of ‘Y’ alone = (90/45) = 2 units/hour

    Efficiency of ‘X’ alone = (5 – 2) = 3 units/hour

    Time taken by ‘X’ to finish the work alone = (90/3) hours = (90/3) × 60 = 1800 minutes

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