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?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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