Question

    A and B together can complete a piece of

    work in 40 days while B and C together can complete the same work in 36 days. All of three together can complete 80% of the whole work in 26.4 days then find the time taken by A and C together to complete the whole work. Note: You have to find approx. value
    A 122 days Correct Answer Incorrect Answer
    B 128 days Correct Answer Incorrect Answer
    C 50 days Correct Answer Incorrect Answer
    D 142 days Correct Answer Incorrect Answer
    E 160 days Correct Answer Incorrect Answer

    Solution

    Time taken by A, B and C together to complete the whole work = 26.4/0.80 = 33 days
    Let total amount of work = 3960 (LCM of 40, 36 and 33)
    Efficiency of (A + B) = 3960/40 = 99 units per day
    Efficiency of (B + C) = 3960/36 = 110 units per day
    Efficiency of (A + B + C) = 3960/33 = 120 units per day
    Efficiency of A = 120 – 110 = 10 units per day
    Efficiency of C = 120 – 99 = 21 units per day
    Desired time = 3960/31 = 127.7 days = 128 days

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