A man rows 30 km downstream in 2 hours and 18 km upstream in 2 hours. What is the speed of the stream?

Explanation

1. 01

   Downstream $\frac{30}{2} = 15$ km/h, upstream $\frac{18}{2} = 9$ km/h.

2. 02

   Stream $= \frac{15 - 9}{2} = 3$ km/h.