Question

    Two pipes A and B can fill a tank in 24 minutes and 36

    minutes, respectively. If both pipes are opened simultaneously, but B is turned off after 12 minutes, how much time will A take to fill the remaining tank?
    A 4 minutes Correct Answer Incorrect Answer
    B 9 minutes Correct Answer Incorrect Answer
    C 10 minutes Correct Answer Incorrect Answer
    D 8 minutes Correct Answer Incorrect Answer

    Solution

    Part filled in 12 minutes by both = 12 × (1/24 + 1/36) = 12 × (3 + 2)/72 = 5/6.  Remaining = 1 - 5/6 = 1/6.  Time taken by A = (1/6) ÷ (1/24) = 4 minutes.  Correct option: a

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