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    Question

    Pipe 'A' is 6 times as efficient as pipe 'B'. Pipe 'C',

    which is one-sixth as efficient as pipe 'B', can fill a tank alone in 18 hours. Find difference between time taken by pipe 'C' to fill 66.67% of the tank and time taken (in minutes) by pipe 'A' to fill the tank completely.
    A 660 minutes Correct Answer Incorrect Answer
    B 690 minutes Correct Answer Incorrect Answer
    C 720 minutes Correct Answer Incorrect Answer
    D 750 minutes Correct Answer Incorrect Answer

    Solution

    Let the efficiency of pipe 'C' be 'x' litres/hour.
    So, total capacity of the tank = '18x' litres.

    Efficiency of pipe 'A' = x × 6 × 6 = '36x' litres/hour
    So, time taken by pipe 'A' to fill the tank = 18x / 36x = 0.5 hours

    And, time taken by pipe 'C' to fill 66.67% of the tank = (18x × 2/3) / x = 12 hours

    So, required difference = 12 - 0.5 = 11.5 hours = 11.5 × 60 = 690 minutes

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