Pipe A can fill a tank in 6 hours, Pipe B can fill it in 8 hours, and Pipe C can empty it in 12 hours. If all three pipes are opened simultaneously, how many hours will it take to fill the empty tank?
✓ Correct Answer: Option B
The combined rate is (1/6) + (1/8) - (1/12) = (4+3-2)/24 = 5/24 tank/hour. The time to fill the tank is the reciprocal of the combined rate: 24/5 = 4.8 hours.