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    Question

    A and B together can complete a task in 12 days, while B

    and C together can complete the same task in 15 days. A and C together take 20 days to finish it. If A, B, and C work together, how many days will they take to complete the task?
    A 8 days Correct Answer Incorrect Answer
    B 9 days Correct Answer Incorrect Answer
    C 10 days Correct Answer Incorrect Answer
    D 11 days Correct Answer Incorrect Answer

    Solution

    1/A + 1/B = 1/12 1/B + 1/C = 1/15 1/A + 1/C = 1/20 Adding the three equations: 2(1/A + 1/B + 1/C) = 1/12 + 1/15 + 1/20 = 1/5 (1/A + 1/B + 1/C) = 1/10 So, the total time = 10 days. Correct Option: c) 10 days

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