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    Question

    Pipes A and B alone can fill a tank in 12 minutes and 18

    minutes, respectively, while pipe C alone can empty the full tank in 36 minutes. If all the pipes are opened together, then find the time taken to fill the tank completely.
    A 9 min Correct Answer Incorrect Answer
    B 12 min Correct Answer Incorrect Answer
    C 25 min Correct Answer Incorrect Answer
    D 18 min Correct Answer Incorrect Answer
    E none of these Correct Answer Incorrect Answer

    Solution

    ATQ, Time taken by pipe C to empty the full tank = 36 minutes. Let the total capacity of the tank = 72 liters (LCM of 12, 18, and 36). Quantity of water filled by pipe A in one minute = 72 / 12 = 6 liters. Quantity of water filled by pipe B in one minute = 72 / 18 = 4 liters. Quantity of water emptied by pipe C in one minute = 72 / 36 = 2 liters. Required time taken = 72 / (6 + 4 - 2) = 72 / 8 = 9 minutes.

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