A man can row 4.5 km/hr in still water and he finds that it takes him twice as…
2023
A man can row 4.5 km/hr in still water and he finds that it takes him twice as long to row up as to row down the river. Find the rate of the stream.
Answer: A. 1.5 km/hr — Solution: Let the speed of the stream be x km/hr. The rower's speed in still water is 4.5 km/hr. Upstream speed = 4.5 - x km/hr; downstream speed = 4.5 + x…
- A.
1.5 km/hr
- B.
1.7 km/hr
- C.
1.4 km/hr
- D.
2.5 km/hr
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Correct answer: A
Solution: Let the speed of the stream be x km/hr. The rower's speed in still water is 4.5 km/hr.
Upstream speed = 4.5 - x km/hr; downstream speed = 4.5 + x km/hr.
For the same distance, time is inversely proportional to speed. Given upstream time is twice the downstream time:
1/(4.5 - x) = 2/(4.5 + x).
Solve the equation: cross-multiply to get 4.5 + x = 2(4.5 - x) = 9 - 2x. Rearranging gives 3x = 4.5, so x = 1.5 km/hr.
Answer: The rate of the stream is 1.5 km/hr.