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    Question

    A tank has two inlet pipes, A and B, which can fill the

    tank in 6 hours and 8 hours, respectively, and an outlet pipe C, which can empty the tank in 12 hours. If all three pipes are opened together, how long will it take to fill the tank?
    A 4 hours Correct Answer Incorrect Answer
    B 4.8 hours Correct Answer Incorrect Answer
    C 5.4 hours Correct Answer Incorrect Answer
    D 6 hours Correct Answer Incorrect Answer

    Solution

    Work done by A in 1 hour = 1/6. Work done by B in 1 hour = 1/8. Work done by C in 1 hour = -1/12. Net work done in 1 hour = (1/6) + (1/8) - (1/12). LCM of 6, 8, and 12 is 24. Net work = (4/24) + (3/24) - (2/24) = 5/24. Time to fill the tank = 24/5 = 4.8 hours. Correct option: b

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