Question

A man rows to a place at a distance of $48$ km and back in $14$ hours. He finds that he can row $4$ km with the stream in the same time as $3$ km against the stream. What is the rate of the stream?

• A. $1$ km/hr
• B. $2$ km/hr
• C. $3$ km/hr
• D. $4$ km/hr

Answer 1

The correct option is A $1$ km/hr

Ratio of the downstream speed to upstream speed $=4:3$
Therefore, ratio of times taken to cover a certain distance downstream and upstream $=3:4$
Given, $3x+4x=14$ hrs

$\Rightarrow$ $x=2$
The man took $6$ hours to row $48$ km downstream and $8$ hours to row $48$ km upstream
Speed downstream $=\frac{48}{6}$ km/hr $=8$ km/hr
Speed upstream $=\frac{48}{8}$ km/hr $=6$ km/hr
Thus rate of stream $=\frac{1}{2}(8-6)$ km/hr $=1$ km/hr