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    Question

    A tank is filled with 3 inlet pipes and 2 outlet pipes.

    Inlet pipes A, B, and C can fill the tank in 6 hours, 8 hours, and 12 hours, respectively. Outlets D and E can empty the tank in 9 hours and 15 hours, respectively. If all the pipes are opened simultaneously, how long will it take to fill the tank?
    A 5 hours Correct Answer Incorrect Answer
    B 6 hours Correct Answer Incorrect Answer
    C 4.5 hours Correct Answer Incorrect Answer
    D 4 hours Correct Answer Incorrect Answer

    Solution

    The rate of A = 1/6, B = 1/8, C = 1/12, D = -1/9, and E = -1/15 (per hour). Combined rate = (1/6 + 1/8 + 1/12 - 1/9 - 1/15) = 71/360  Time taken to fill the tank = 360/71 hours. = 5 hours(approx) Answer: a) 5 hours

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