Question

A swimmer aids his body north directly across a 80m river at a speed of 12m/s. If the river is moving west at 0.7m/s. How far down stream will he land and how long will it take him to cross the river

Answer 1

Calculate the time required to cross the river:

$$t=\frac{w}{v}=\frac{80}{12}=6.67\text{ s}.$$

Find how far down stream he will land:

$$d=ut=0.7\cdot6.67=4.67\text{ m}.$$