Question

A tank is fitted with 2 taps , first tap can completly fill the tank in 45 minutes and second tank can empty the full tank in 1 hour. If both the taps are opened alternatively for one minute, then in how many hours empty tank will be filled completely ?

Answer 1

1st minute=1/45
2nd minute=-1/60 
End results of the two minutes=1/45-1/60=4/180-3/180=1/180 
At the end of 358 minutes=179/180
Remaining amount of work=1/180
Time=1/180÷1/45=1/4minutes
=358.25 minutes