A swimmer goes from A to B in 4 hr and return back from B to A in only 2 hr. find velocity of river flow and velocity of swimmer in still water.

Question

A swimmer goes from A to B in 4 hr and return  back from B to A in only 2 hr. find velocity of river flow and velocity of swimmer in still water.

anonymous · Answer

Let the velocity of the river be $v_r$ and the velocity of the swimmer be $v_s$.  Let the time to to go the first trip be $\Delta t_{AB}$ and the time for the reverse trip be $\Delta t_{BA}$.  Let the distance between point $A$ and $B$ be $\ell$.  By the definition of constant velocity, we can write the two following equations that you can use to solve for the velocities.$$v_s-v_r=\frac{\ell}{\Delta t_{AB}}$$$$v_s+v_r=\frac{\ell}{\Delta t_{BA}}$$

anonymous · Answer

i think it go over my head.can u xplain it more clearly/.

anonymous · Answer

Oops, I forgot the distance,

x-> speed of the man in still water
y-> speed of the river current

$x+y =\frac l 4$

$x-y =\frac l 2 $

anonymous · Answer

@Ruchi.  What is confusing you about my post?

anonymous · Answer

i hav nt understood it clearly what ever u hav written @yakeyglee

anonymous · Answer

What trips you up?