A pipe can fill a tank in 120 minutes while the drain can drain it in 150 minutes. If the drain is left open and the fill pipe is turned on, how long will it take to fill the tub?

600 minutes or 10 hours

Step-by-step explanation:

We can solve this problem by looking at the net increase per minute. To find this, we can set rates for each value.

The pipe will be able to fill 1/120 of the tank in a minute, and the drain will drain 1/150 in a minute. So subtract the two:

1/120 - 1/150 = 1/600 of the tank per minute

Therefore you need 600 minutes to fill the tank, or 10 hours.