Question

    Three pipes A, B, and C can fill a tank in 15 hours, 20

    hours, and 25 hours respectively. All three pipes are opened together, but after 4 hours, pipe C is closed. How much more time will it take to fill the tank completely?
    A 6 hours Correct Answer Incorrect Answer
    B 5.5 hours Correct Answer Incorrect Answer
    C 3.2 hours Correct Answer Incorrect Answer
    D 7 hours Correct Answer Incorrect Answer
    E 6.5 hours Correct Answer Incorrect Answer

    Solution

    Calculate the combined rate of all three pipes (A, B, C):

    Work done in the first 4 hours (all pipes open):

    Remaining work:

    Rate after closing pipe C (only A and B):

    Time to complete remaining work:

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