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    Question

    Two pipes A and B fill a square tank in 28 and 36 hours respectively while a third pipe C can empty it in 63 hours If all three pipes are opened together then what time will they take to fill the tank?

    A 21 Correct Answer Incorrect Answer
    B 28 Correct Answer Incorrect Answer
    C 36 Correct Answer Incorrect Answer
    D 31 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Alternate Method: Let leak = C A B A+B+C Time 28 36 63 Let capacity of total tank = LCM (28,36 & 63) = 7*9*4 L Eff 9 : 7 : 4 So Leak can empty in 1 hr = A+B+C - (A+B) = 4 - (9+7) = 4 - 16 = -12 L Hence leak can empty the tank in = 7*9*4/12 = 21 hours

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