A pump can fill a tank in 2 hours. However, due to a leak, it actually takes 2 hours and 20 minutes to fill the tank. How long will the leak take to empty the full tank on its own?

Explanation

The pump fills the tank at a rate of 1/2 per hour. With the leak, the effective filling rate is 1/(7/3) = 3/7 per hour. Therefore, the leak's draining rate is the difference: (1/2) - (3/7) = 1/14. This means the leak alone can empty the tank in 14 hours.