Question: If a tank is filled by a pipe in 5 hours and another pipe can empty it in 10 hours, how long will it take to fill the tank if both pipes are opened for 2 hours?
Options:
Correct Answer: 3 hours
Solution:
In 2 hours, the filling pipe fills 2/5 of the tank and the emptying pipe empties 2/10 of the tank. Net filled = 2/5 - 1/5 = 1/5. Therefore, 1/5 of the tank is filled.