Two pipes can fill a tank individually in 20 hours and 30 hours, respectively. When both pipes are opened together, a leak appears in the tank that causes one-third of the water supplied by the pipes to escape. How long will it take to fill the tank completely under these conditions?

Explanation

The combined filling rate of the two pipes is 1/20 + 1/30 = 1/12 of the tank per hour. Due to the leak, only two-thirds of the supplied water remains, so the effective filling rate is (2/3) × (1/12) = 1/18. To fill the entire tank, time required = 1 ÷ (1/18) = 18 hours. However, since the problem states one-third of water leaks out, the actual calculation considers the net filling rate as two-thirds of the total input. Therefore, the total time taken is 16 hours.