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    Question

    Pipe 'Q' can fill a tank in 20 hours, while Pipe 'R'

    completes the job in 15 hours. If both pipes are operated simultaneously, how long will it take for them to fill the tank?
    A 8 hrs Correct Answer Incorrect Answer
    B 9(4/7) hrs Correct Answer Incorrect Answer
    C 8(4/7) hrs Correct Answer Incorrect Answer
    D 7(4/7) hrs Correct Answer Incorrect Answer

    Solution

    Total capacity of tank = 60 {LCM of 20 and 15} Efficiency of pipe 'Q' = 60/20 = 3 units per hr Efficiency of pipe 'R' =  60/15 = 4 units per hr Required time = 60/7 = 8(4/7) hrs Hence, option c.

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