Pipe A can fill an empty cistern in 4 hours while along with Pipe B it can fill it up in 3 hours. Only Pipe A is turned on for an hour after which Pipe B is also turned on. How much total time will it take to fill up the cistern?
A
3 hrs 20 min
B
3 hrs 25 min
C
3 hrs 15 min
D
3 hrs
Correct Answer: 3 hrs 15 min