Question

    In what time would a cistern be filled by three pipes

    whose diameter are 2cm, 2*2/3cm, 4cm running together, when the largest pipe alone fill the cistern in 122 minutes the amount of water flowing in  by each pipe being proportional to the square of diameter?
    A 64 minutes Correct Answer Incorrect Answer
    B 68 minutes Correct Answer Incorrect Answer
    C 72 minutes Correct Answer Incorrect Answer
    D 78 minutes Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Total Efficiency = 9 + 16 + 36 = 61 Pipe 3rd alone can fill the cistern in 122 min (given) ∴ Capacity of the tank = (36 × 122) = 4392 Time taken by all pipes together = 4392/(61 )= 72 minutes

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