A river is flowing from W to E with a speed of 5 m/min. A man can swim in still water with a velocity 10 m/min. In which direction should the man swim so as to take the shortest possible path to go to the south.

The correct option is C 120° with downstream

For shortest possible path man shouls swim with an angle $(90+\theta$) with downstream.

Frm the fig, $sin\theta =\frac{vr}{vm}=\frac{5}{10}=\frac{1}{2}\Rightarrow \therefore \theta ={30}^{\circ }$

So angle with downstream $={90}^{\circ }+{30}^{\circ }={120}^{\circ }$