When the water is turned on, a bathtub will be filled in 12 minutes. When the drain is opened it tak

When the water is turned on, a bathtub will be filled in 12 minutes. When the drain is opened it takes 20 minutes for the tub to drain. If the water is turned on and the drain is left open, how long until the tub is filled?

In one hour, the faucet will fill 5 tubs since 12 * 5 = 60 minutes.
In one hour, the drain will empty 3 tubs since 20 * 3 = 60 minutes
The difference is 2 tubs filled per hour.

Therefore, we have 1 tub filled in 1/2 hour or 30 minutes