Question

Pipe P can fill a tank by itself in 16 hours, while pipe R can empty the tank in 36 hours when it is full. Together, pipes P and Q can fill the tank in 9 hours. How long will it take for pipes Q and R, working together, to fill the same tank?

Q: Answer-Pipe P can fill a tank by itself in 16 hours, while pipe R can empty the tank in 36 hours when it is...

ATQ, Let the capacity of the tank L.C.M of 16 and 36 144 units Then, efficiency of pipe P alone 144 16 9 unitshour Efficiency of pipe R alone 144 36 4 unitshour Combined efficiency of pipes P and Q 144 9 16 unitshour So, efficiency of pipe Q alone 16 9 7 unitshour So, combined efficiency of pipes Q and R 7 4 3 unitshour So, time taken by pipes Q and R together to ill the tank 144 3 48 hours.