Two pipes can fill a tank in 10hours and 12 hours respectively while a third, pipe empties the full tank in 20 hours. If all the three pipes operate simultaneously, in how much time will the tank be filled?
A. 7 hrs
B. 7 hrs 30 min
C. 5 hrs
D. 5 hrs 30 min
Correct Answer :
B. 7 hrs 30 min
Net part filled In 1 hour =(1/10)+(1/12)-(1/20)=(8/60)=(2/15).