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    Question

    Pipes 'J' and 'K' can fill a tank in 12 hours and 18

    hours respectively, while pipe 'L' can empty it in 36 hours. All pipes are opened together when the tank was empty. After 2 hours, pipe 'J' is closed. Find the total time taken to fill the tank.
    A 12 hrs Correct Answer Incorrect Answer
    B 25 hrs Correct Answer Incorrect Answer
    C 30 hrs Correct Answer Incorrect Answer
    D 18 hrs Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Tank capacity = 180 units Efficiency of pipe 'J' = 180 / 12 = 15 units/hour Efficiency of pipe 'K' = 180 / 18 = 10 units/hour Efficiency of pipe 'L' = 180 / 36 = 5 units/hour Tank filled in 2 hours = (15 + 10 - 5) × 2 = 40 units Time taken by pipes 'K' and 'L', together to fill the remaining part of tank = (180 - 40) / (10 - 5) = 28 hours Total time taken = 2 + 28 = 30 hours

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