Question: A tank can be filled by a pipe in 4 hours and emptied by another pipe in 8 hours. If both pipes are opened together, how long will it take to fill the tank?
Options:
Correct Answer: 5 hours
Solution:
The net rate is 1/4 - 1/8 = 2/8 - 1/8 = 1/8. Therefore, it will take 8 hours to fill the tank.