Question

A river is flowing from west to east at a speed of $5\text{metres per minute}$. A man on the south bank of the river, capable of swimming at $10\text{metres per minute}$ in still water, wants to swim across the river in the shortest time. He should swim in a direction

Answer 1

We know that,

For minimum time, the swimmer should swim perpendicular to the direction of river flow, so that all his/her energy or velocity will be directed towards crossing the river. So, he should swim due north.

Hence, option $\left(\text{A}\right)$ is the correct answer.