A man rows downstream 30 km and upstream 20 km. If he takes 5 hours to cover each distance, then the speed of stream is

1 km/hr

The correct answer is Option (2) → 1 km/hr **

Let the speed of the man in still water be $x$ km/h and the speed of the stream be $y$ km/h.

Downstream speed $=(x+y)$ and upstream speed $=(x-y)$.

Given:

$\frac{30}{x+y}=5$ and $\frac{20}{x-y}=5$

$\Rightarrow x+y=6$ and $x-y=4$

Adding both equations:

$2x=10 \Rightarrow x=5$

Substituting in $x+y=6$ gives $y=1$.

Speed of stream = 1 km/h