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    Question

    Two pipes, A and B, can independently fill the tank in 15 minutes and 20 minutes respectively, while pipe C can empty 7 gallons from the tank in 2 minutes. If all three pipes are operated simultaneously, and they manage to fill the tank in 12 minutes, what is the tank's capacity?

    A 120 Correct Answer Incorrect Answer
    B 300 Correct Answer Incorrect Answer
    C 105 Correct Answer Incorrect Answer
    D 450 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Taking LCM of 15, 20 and 12 = 60 Efficiency of A = 4 Efficiency of B = 3 Efficiency of (A+B-C) = 5 Efficiency of C = (4 + 3) – 5 = -2 Pipe C empty the tank in = 60/2 = 30 min Capacity of the tank = 30 × (7/2) = 105 gallons

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