Two taps fill a tank in 6 and 8 hours, and an outlet empties it in 12 hours. All three are opened together. How long does the tank take to fill?

Explanation

1. 01

   Net rate $= \frac{1}{6} + \frac{1}{8} - \frac{1}{12} = \frac{4 + 3 - 2}{24} = \frac{5}{24}$.

2. 02

   So $\frac{24}{5} = 4.8$ hours.