Question

The speed of a swimmer is $4 km h ^{-1}$ in still water If the swimmer makes his strokes normal to the flow of river of width $1 km$, he reaches a point $750 m$ down the stream on the opposite bank.The speed of the river water is ___ $km h ^{-1}$

Answer 1

Correct Answer: 3

The correct answer is 3

time to cross the River width $\omega =1000m$
$\text{is}=\frac{1km}{4km/h}$
Drift $x=Vm/g\times t$
Where $Vm/g$ is velocity of River w.r. to ground.
$x=Vm/g\times \frac{1}{4}=750m=\frac{3}{4}km$
$Vm/g=3km/hr$