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    Question

    Pipes ‘P’ and ‘Q’ alone can fill a tank in 10

    minutes and 25 minutes, respectively, while pipe ‘R’ can empty the same tank in 50 minutes. If all three pipes are opened together, then find the time taken to fill the tank.
    A 4 mins 20 secs Correct Answer Incorrect Answer
    B 9 mins 20 secs Correct Answer Incorrect Answer
    C 12 mins 20 secs Correct Answer Incorrect Answer
    D 8 mins 20 secs Correct Answer Incorrect Answer

    Solution

    ATQ,
    Let the capacity of the tank be 50 litres {LCM (10, 25, and 50)}
    Efficiency of pipe ‘P’ = (50/10) = 5 litres/minute
    Efficiency of pipe ‘Q’ = (50/25) = 2 litres/minute
    Efficiency of pipe ‘R’ = (50/50) = 1 litre/minute
    Required time = {50 / (5 + 2 – 1)} = 50/6 = 25/3
    The tank will be filled in 25/3 min or 8 minutes and 20 seconds.

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