Question: If a tank can be filled by a pipe in 4 hours and emptied by another pipe in 6 hours, how long will it take to fill the tank if both pipes are opened together?
Options:
Correct Answer: 2 hours
Solution:
The net rate is 1/4 - 1/6 = 3/12 - 2/12 = 1/12. Therefore, it will take 12 hours to fill the tank.