A boatman takes 3 hours 45 minutes to travel 15 km downstream and takes 2…
2025
A boatman takes 3 hours 45 minutes to travel 15 km downstream and takes 2 hours 30 minutes to travel 5 km upstream of a river. What is the speed of the stream of the river in km/h?
- A.
2 km/h
- B.
1 km/h
- C.
6 km/h
- D.
4 km/h
Attempted by 16 students.
Show answer & explanation
Correct answer: B
Answer:
1 km/h
Explanation:
Downstream:
Time taken = 3 + 45/60 = 3 + 3/4 = 15/4 h.
Distance covered = 15 km.
Downstream Speed = 15 / (15/4) = 4 km/h.
Upstream:
Time taken = 2 + 30/60 = 2 + 1/2 = 5/2 h.
Distance covered = 5 km.
Upstream Speed = 5 / (5/2) = 2 km/h.
We know, speed of stream
= 1/2 (Downstream Speed – Upstream Speed)
= 1/2 (4-2) = 1 km/h.