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    Question

    Pipe E can fill a tank in 40 minutes while pipe F can

    fill the same tank in 50 minutes. If pipe E and F are opened simultaneously, then after how much time must pipe E be closed so that the whole tank is filled in 25 minutes?
    A 162 min Correct Answer Incorrect Answer
    B 100 min Correct Answer Incorrect Answer
    C 140 min Correct Answer Incorrect Answer
    D 172 min Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let the capacity of the tank = 200 liters (LCM of 40 and 50). Quantity of water filled by pipe E in one minute = 200 / 40 = 5 liters. Quantity of water filled by pipe F in one minute = 200 / 50 = 4 liters. Let pipe E be closed after ‘x’ minutes. So, 5x + 4 × (25 – x) = 200 5x + 100 - 4x = 200 x = 100 x = 100/1 x = 100 So, pipe E must be closed after 100 minutes.

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