Question

    A person can complete a work in 15 days, and another

    person can complete the same work in 20 days. They work together for 5 days, and then the first person leaves. How many more days will it take for the second person to complete the remaining work?
    A 5 Correct Answer Incorrect Answer
    B 6 Correct Answer Incorrect Answer
    C 7 Correct Answer Incorrect Answer
    D 8.3 Correct Answer Incorrect Answer
    E 9 Correct Answer Incorrect Answer

    Solution

    Work done by the first person in 1 day = 1/15. Work done by the second person in 1 day = 1/20. Together, in 1 day, they can complete = 1/15 + 1/20  = 4/60 + 3/60 = 7/60 of the work. In 5 days, they will complete = 5 × 7/60 = 35/60 = 7/12 of the work. Remaining work = 1 - 7/12 = 5/12. The second person alone will complete 1/20 of the work per day. Time required for the second person to complete the remaining work  = (5/12) ÷ (1/20)  = 5/12 × 20 = 8.33 days. Correct answer: d. 8.3

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