A man rows 15 km upstream in 5 hours and 25 km downstream in 5 hours each time, then the speed of the stream is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 1 km / hour
Let u be the speed of the man in still water and v the speed of the stream (km/hour). Upstream the stream slows him down; downstream it helps him:
\( \displaystyle u - v = \frac{15}{5} = 3 \)
\( \displaystyle u + v = \frac{25}{5} = 5 \)
Subtracting the first equation from the second:
\( 2v = 2,\quad v = 1 \text{ km/hour} \)
CBSE Applied Mathematics (Class XII):
Boats and Streams
