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    Question

    Pipe ‘A’ can fill a tank in 14 hours whereas pipe

    ‘B’ can empty it in 28 hours. If both pipes are opened together while pipe ‘B’ is closed after 6 hours, then find the time taken by pipe ‘A’ to fill the rest of the tank.
    A 12 hrs Correct Answer Incorrect Answer
    B 11 hrs Correct Answer Incorrect Answer
    C 19 hrs Correct Answer Incorrect Answer
    D 15 hrs Correct Answer Incorrect Answer

    Solution

    ATQ; Let the capacity of the tank be 28 litres. {LCM (14 and 28)} Efficiency of inlet pipe ‘A’ = (28/14) = 2 litres/hour Efficiency of outlet pipe ‘B’ = (28/28) = 1 litre/hour Combined efficiency of both pipes = (2 – 1) = 1 litre/hour Required time = {28 – (1 × 6)} ÷ 2 = 11 hours

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