A boat takes an hour to cover a certain distance downstream in a river. It…
2025
A boat takes an hour to cover a certain distance downstream in a river. It takes 1 1/2 hour to cover the same distance upstream. Assuming that the speed of boat is same in both downstream and upstream directions, what is the ratio of speed of boat to that of stream in the river?
- A.
2 : 3
- B.
5 : 1
- C.
3 : 2
- D.
5 : 2
Attempted by 3 students.
Show answer & explanation
Correct answer: B
Let the speed of the boat be B and the speed of the stream be S.
Downstream speed = B + S, Upstream speed = B - S.
Distance is constant. Downstream time = 1 hour, Upstream time = 1.5 hours.
(B + S) × 1 = (B - S) × 1.5
2(B + S) = 3(B - S)
2B + 2S = 3B - 3S
5S = B
Therefore, the ratio of boat speed to stream speed is B:S = 5:1.