A man rows 24 km upstream in 6 hours and 36 km downstream in 6 hours each time, then the speed of the boat in the still water is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 5 km/hr
Let u be the speed of the boat in still water and v the speed of the stream. Then the upstream speed is u − v and the downstream speed is u + v:
\( \displaystyle u - v = \frac{24}{6} = 4 \text{ km/hr} \)
\( \displaystyle u + v = \frac{36}{6} = 6 \text{ km/hr} \)
Adding the two equations:
\( \displaystyle u = \frac{4 + 6}{2} = 5 \text{ km/hr} \)