Question

    A pipe fills a tank in 20 hours, and another pipe

    empties it in 30 hours. If both pipes are opened together, how long will it take to fill the tank?
    A 70 hours Correct Answer Incorrect Answer
    B 120 hours Correct Answer Incorrect Answer
    C 40 hours Correct Answer Incorrect Answer
    D 60 hours Correct Answer Incorrect Answer

    Solution

    The rate of the filling pipe is 1/20. The rate of the emptying pipe is 1/30. Net rate = (1/20 - 1/30) = 1/60. Time taken = 60 hours. Correct Option: d) 60 hours

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