Question

A swimmer swims in still water at a speed of $5km/hr$. He enters a $200m$ wide river, having a river flow speed of $4km/hr$. He proceeds to swim at an angle of ${127}^{\circ }$ with the river flow direction. He reaches directly opposite to the starting point and then swims with the river flow to cover a distance of $200m$. The total time taken by the swimmer to complete his journey is

• A. $5min$
• B. $4min$
• C. $3min$
• D. $6min$

Answer 1

The correct option is D $6min$

Given, width of the river $d=200m$
velocity of the river $V_r=4km/hr$
and, velocity of swimmer in still water $V_{sr}=5km/hr$

As per the question, time taken by swimmer to reach directly opposite side is
$t_1=\frac{d}{5cos{37}^{\circ }}=\frac{0.2}{4}hr=3min$
Also, the swimmer swims with the river flow to cover the distance $200m$, time taken by him for this is
$t_2=\frac{0.2}{4}hr=3min$
Thus, total journey time is $t_1+t_2=6min$