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    Question

    A tank has two inlet pipes and one outlet pipe. Pipe A

    can fill the tank in 4 hours, and Pipe B can fill it in 6 hours. The outlet pipe C can empty the tank in 8 hours. If all three pipes are opened simultaneously, how much time will it take to fill the tank completely?
    A 4 hours Correct Answer Incorrect Answer
    B 5 hours Correct Answer Incorrect Answer
    C 3.5 hours Correct Answer Incorrect Answer
    D 4.5 hours Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Pipe A’s rate = 1/4 tank per hour. Pipe B’s rate = 1/6 tank per hour. Pipe C’s rate = -1/8 tank per hour (negative because it empties the tank). Net rate = (1/4 + 1/6 - 1/8) = (6 + 4 - 3)/24 = 7/24 tank per hour. Time taken to fill the tank = 1 / (7/24) = 24/7 hours ≈ 3.43 hours  Correct option: E) None of these

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