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
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1 km/hr
Let the speed of the man in still water be u km/hr and the speed of the stream be v km/hr. The downstream speed is \(u + v\) and the upstream speed is \(u - v\), so
\( \displaystyle u + v = \frac{30}{5} = 6 \)
\( \displaystyle u - v = \frac{20}{5} = 4 \)
Subtracting the second equation from the first:
\(2v = 2\)
\(v = 1\)
So the speed of the stream is 1 km/hr (and the man rows at 5 km/hr in still water).
CBSE Applied Mathematics (Class XII):
Boats and Streams
