Question

Tap A can fill an empty cistern in 2 hours while the outlet pipe B can empty it in 3 hours how long will it take to fill the cistern if both the taps and pipes are opened simultaneously

Answer 1

In one hour part of cistern filled by tap A=1/2

Part of cristen emptied by outlet B=1/3

Total parts filled when both of them are opened together=1/2-1/3
=1/6
So time taken to fill the cistern will be 6hours