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    Question

    An inlet can fill an empty tank in 7 hours whereas an

    outlet pipe can empty it in 14 hours. If (N - 1) such outlet pipes having same efficiency and (N + 2) such inlet pipes having same efficiency are opened together, then the tank gets filled in 2 hours. How many inlet pipes are used?
    A 2 Correct Answer Incorrect Answer
    B 4 Correct Answer Incorrect Answer
    C 5 Correct Answer Incorrect Answer
    D 8 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let the capacity of the tank be 14 litres (LCM of 7 and 14). Efficiency of 1 inlet pipe = 14/7 =2 units/hour Efficiency of 1 outlet pipe = (14/14)=1 units/hour According to the question, Required number of inlet pipes used = N+2 = 2+2 = 4

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