A boat goes 48 km downstream in 3 hours and returns the same distance upstream in 4 hours. What is its speed in still water?

Explanation

1. 01

   Downstream $\frac{48}{3} = 16$ km/h; upstream $\frac{48}{4} = 12$ km/h.

2. 02

   Still water $= \frac{16 + 12}{2} = 14$ km/h.