A man rows 750 m in 675 seconds against the stream and returns in 7 and half…
2023
A man rows 750 m in 675 seconds against the stream and returns in 7 and half minutes. His rowing speed in still water is
- A.
4 kmph
- B.
5 kmph
- C.
6 kmph
- D.
7 kmph
Attempted by 15 students.
Show answer & explanation
Correct answer: B
Step 1: Convert distance and times to speeds.
Distance each way = 750 m = 0.75 km.
Time against the stream = 675 s = 675/3600 hr = 0.1875 hr. Upstream speed = 0.75 / 0.1875 = 4 km/h.
Time with the stream = 7.5 minutes = 450 s = 450/3600 hr = 0.125 hr. Downstream speed = 0.75 / 0.125 = 6 km/h.
Step 2: Find the rowing speed in still water.
The rowing speed in still water is the average of upstream and downstream speeds: (4 + 6) / 2 = 5 km/h.
Answer: 5 kmph