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    Question

    A can complete a work in 10 days and B can complete the

    same work in 15 days. They work together for 2 days and then B alone finishes the remaining work. In how many total days is the work completed?
    A 20 days Correct Answer Incorrect Answer
    B 12 days Correct Answer Incorrect Answer
    C 18 days Correct Answer Incorrect Answer
    D 17 days Correct Answer Incorrect Answer

    Solution

    A’s 1-day work = 1/10 B’s 1-day work = 1/15 Together in 1 day = 1/10 + 1/15 = (3 + 2) / 30 = 5/30 = 1/6 Work done in 2 days together = 2 × 1/6 = 1/3 Remaining work = 1 − 1/3 = 2/3 Now only B works: B’s 1-day work = 1/15 Time to do 2/3 work = (2/3) ÷ (1/15) = (2/3) × 15 = 10 days Total time = 2 + 10 = 12 days

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