A tank can be filled by one pump in 3.2 hours and by another pump in 80 minutes. A third pump can drain the tank in 2 hours and 20 minutes. If all 3 pumps go into operation, how long will it take to fill the tank?
+36916 1 tank / 3.2 hr = rate 1
1 tank / 1.33 hr = rate 2
- 1tank/2.33 hr = rate 3
1 / (1/3.2 + 1/1.33 - 1/2.33) = 1.574 hr for 1 tank to be filled with all three running
