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    Question

    A can complete a certain work in 12 days, while B can

    complete it in 15 days. After working together for 4 days, A leaves and B continues working alone. How many additional days will B take to finish the remaining work?
    A 8 days Correct Answer Incorrect Answer
    B 6 days Correct Answer Incorrect Answer
    C 12 days Correct Answer Incorrect Answer
    D 15 days Correct Answer Incorrect Answer

    Solution

    A's work rate = 1/12, B's work rate = 1/15 Combined work rate = 1/12 + 1/15 = (5 + 4) / 60 = 9/60 = 3/20 Work done in 4 days = 4 * (3/20) = 12/20 = 3/5 Remaining work = 1 - 3/5 = 2/5 B's work rate = 1/15, so time taken by B = (2/5) / (1/15) = (2/5) * 15 = 6 days

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