A man goes upstream for 24km in 2 hour. Another man goes downstream for same…
2023
A man goes upstream for 24km in 2 hour. Another man goes downstream for same distance in 1 hour. If speed of stream is 8 km/hr. What is the difference in speed of both men ?
- A.
5 kmph
- B.
3 kmph
- C.
4 kmph
- D.
6 kmph
Attempted by 17 students.
Show answer & explanation
Correct answer: C
Answer: 4 kmph
Let the speed of the first man in still water be u1 km/h and the second man be u2 km/h. Speed of the stream = 8 km/h.
Upstream: effective speed = distance/time = 24/2 = 12 km/h. So u1 - 8 = 12, giving u1 = 12 + 8 = 20 km/h.
Downstream: effective speed = distance/time = 24/1 = 24 km/h. So u2 + 8 = 24, giving u2 = 24 - 8 = 16 km/h.
Difference in their speeds in still water = 20 - 16 = 4 km/h.