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    Question

    Pipes ‘X’ and ‘Y’ alone can fill a tank in 12

    minutes and 18 minutes, respectively, while pipe ‘Z’ can empty the same tank in 36 minutes. If all three pipes are opened together, then find the time taken to fill the tank.
    A 4 mins Correct Answer Incorrect Answer
    B 9 mins Correct Answer Incorrect Answer
    C 12 mins Correct Answer Incorrect Answer
    D 20 mins Correct Answer Incorrect Answer

    Solution

    ATQ,
    Let the capacity of the tank be 72 litres {LCM (12, 18, and 36)}
    Efficiency of pipe ‘X’ = (72/12) = 6 litres/minute
    Efficiency of pipe ‘Y’ = (72/18) = 4 litres/minute
    Efficiency of pipe ‘Z’ = (72/36) = 2 litres/minute
    Required time = {72 / (6 + 4 – 2)} = 9 minutes

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