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    Question

    A and B can do a job in 20 days and 30 days,

    respectively. A and B work together for 5 days, and then A leaves. After how many more days will B complete the remaining work?
    A 15 days Correct Answer Incorrect Answer
    B 16 days Correct Answer Incorrect Answer
    C 17.5 days Correct Answer Incorrect Answer
    D 20 days Correct Answer Incorrect Answer

    Solution

    Work done by A per day = 1/20, Work done by B per day = 1/30. In 5 days, work done by A and B together = 5 × (1/20 + 1/30) = 5 × (3/60 + 2/60) = 5 × 5/60 = 25/60 = 5/12 of the work. Remaining work = 1 - 5/12 = 7/12 of the work. Now, B will complete the remaining work alone. Work done by B per day = 1/30. Time taken by B to complete the remaining work = (7/12) ÷ (1/30) = (7/12) × 30 = 17.5 days. Correct option: c

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