Two pipes together fill a cistern in 8 hours. One of them alone fills it in 12 hours. How long does the other take alone?

Explanation

1. 01

   The other's rate $= \frac{1}{8} - \frac{1}{12} = \frac{3 - 2}{24} = \frac{1}{24}$.

2. 02

   So it takes 24 hours alone.