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    Question

    A tank has two inlet pipes A and B and an outlet pipe C.

    Pipe A can fill the tank in 6 hours, and Pipe B can fill it in 8 hours. Pipe C can empty the full tank in 4 hours. If all three pipes are opened together, how long will it take to fill the tank completely?
    A 10 hours Correct Answer Incorrect Answer
    B 12 hours Correct Answer Incorrect Answer
    C 15 hours Correct Answer Incorrect Answer
    D 16 hours Correct Answer Incorrect Answer
    E 20 hours Correct Answer Incorrect Answer

    Solution

    Rate of Pipe A = 1/6 per hour Rate of Pipe B = 1/8 per hour Rate of Pipe C = -1/4 per hour Net rate = (1/6) + (1/8) - (1/4) LCM of 6, 8, and 4 = 24 Net rate = (4/24) + (3/24) - (6/24) = 1/24 Time taken = 1 ÷ (1/24) = 24 hours Correct Option: e

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