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    Question

    Pipe β€˜A’ takes 20 minutes to fill a tank. Pipe

    β€˜B’ takes 35 minutes to empty the same tank. If pipe β€˜B’ is opened 17 minutes after pipe β€˜A’, then find the total time taken to fill the tank in this manner.
    A 10 minutes Correct Answer Incorrect Answer
    B 12 minutes Correct Answer Incorrect Answer
    C 15 minutes Correct Answer Incorrect Answer
    D 24 minutes Correct Answer Incorrect Answer

    Solution

    Let the capacity of the tank be β€˜140’ litres {LCM (20, 35)} Efficiency of pipe β€˜A’ = (140/20) = 7 litres/minute Efficiency of pipe β€˜B’ = (140/35) = 4 litres/minute Quantity of water filled by pipe β€˜A’ in 17 minutes = 17 Γ— 7 = 119 litres Quantity of water to be filled = 140 – 119 = 21 litres Time taken by pipe β€˜A’ and β€˜B’ together to fill 21 litres of water = {21/(7 – 4)} = 7 minutes Total time taken = 17 + 7 = 24 minutes

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