Question

An inlet pipe can fill a tank in 10 minutes. A drain can empty the tank in 12 minutes. If the tank is empty and both pipe and drain are open, how long will it be before the tank overflows?

Answer 1

Total Volume = volume in - volume out each minute.

Tv = 1/10 - 1/12 per minute.
Tv = (12 - 10)/120 = 2/120 = 1/60 per minute.

After 60 minutes, the tank should be overflowing.

Answer 2

Excellent answer amistre64! Wow.