Question

A swimmer's speed in the direction of flow of river is $16km{h}^{-1}.$ Against the direction of flow of river, the swimmer's speed is $8km{h}^{-1}.$ Calculate the swimmer's speed in still water and the velocity of flow of the river.

• A. $12kmph,4kmph$
• B. $10kmph,3kmph$
• C. $10kmph,4kmph$
• D. $12kmph,2kmph$

Answer 1

The correct option is A $12kmph,4kmph$

Let the velocity of swimmer in still water be $V_{sr}$ and velocity of river flow be $V_r$
Then, as per question $V_r+V_{sr}=V_s$

$\therefore$ The swimmer's speed along the direction of flow of river water is
$V_r+V_{sr}=16...\left(1\right)$
The swimmer's speed against the flow of the river water is
$V_{sr}-V_r=8...\left(2\right)$
from equations $\left(1\right)$ and $\left(2\right)$
$V_{sr}=12km/h$
$V_r=4km/h$