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    Question

    Pipe 'A' can fill a water tank in 6 hours, while pipe

    'B' requires 8 hours to do the same. When a third pipe, 'C', also contributes, the tank is filled in 160 minutes. Determine how long it would take for pipe 'C' to fill the tank on its own.
    A 12 hours Correct Answer Incorrect Answer
    B 10 hours Correct Answer Incorrect Answer
    C 24 hours Correct Answer Incorrect Answer
    D 15 hours Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    160 minutes = 160/60 = (8/3) hours Let the capacity of water tank be 24 units (LCM of 6, 8 and 8/3). Efficiency of pipe ‘A’ = 24/6 = 4 units/hr Efficiency of pipe ‘B’ = 24/8 = 3 units/hr Efficiency of pipes ‘A’, ‘B’ and ‘C’ together = 24/(8/3) = 9 units/hr Efficiency of pipe ‘C’ = 9 – 4 – 3 = 2 units per hour Required time taken by pipe ‘C’ = 24/2 = 12 hours 

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