Two pipes can fill a tank in 10 hours 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. 4 hrs 30 min
B. 7 hrs 30 min
C. 8 hrs 10 min
D. None of these
Answer:B
Two pipes can fill a tank in 10 hours 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. 4 hrs 30 min B. 7 hrs 30 min C. 8 hrs 10 min D. None of these
Explanation: Net part filled in 1 hour = (1/10) + (1/12)-(1/20) = (8/60) = (2/15).