Discussion Forum

A man can row $7\frac{1}{2}$ kmph in still water. If in a river running at 1.5 km an hour, it takes him 50 minutes to row to a place and back, how far off is the place ?

Answer:

Explanation:

Speed downstream $=(7.5+1.5)$ kmph $=9$ kmph,

Speed upstream $=(7.5-1.5)$ kmph $=6$ kmph. 

Let the required distance be $x$ km.

Then, $\frac{x}{9}+\frac{x}{6}$ $=\frac{50}{60}$

$\Leftrightarrow 2x+3x$ $=\left(\frac{5}{6}\times 18\right) $

$\Leftrightarrow 5x$ $=15$ $\Leftrightarrow x= 3$

Hence, the required distance is 3 km.