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    Question

    Inlet pipes 'A', 'B' fill a tank in 30 and 15 minutes

    respectively. Outlet pipe 'C' is 50% less efficient than A. ‘A’ and ‘C’ work for 15 minutes, then 'A' is replaced with 'B'. Find total time to fill the tank.
    A 25 minutes Correct Answer Incorrect Answer
    B 28 minutes Correct Answer Incorrect Answer
    C 30 minutes Correct Answer Incorrect Answer
    D 33 minutes Correct Answer Incorrect Answer

    Solution

    Tank = 30x units
    A = x, B = 2x, C = 0.5x
    15 mins: (x - 0.5x) × 15 = 7.5x
    Remaining = 30x - 7.5x = 22.5x
    Net = 2x - 0.5x = 1.5x
    Time = 22.5x / 1.5x = 15 minutes
    Total time = 15 + 15 = 30 minutes

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