The speed of a boat in still water is 4 km/h and the speed of current is 2…
2023
The speed of a boat in still water is 4 km/h and the speed of current is 2 km/h. If the time taken to reach a certain distance upstream is 9 hours, the time it will take to go the same distance downstream is
- A.
3.5 hours
- B.
2.5 hours
- C.
2 hours
- D.
3 hours
Attempted by 26 students.
Show answer & explanation
Correct answer: D
Answer: 3 hours
Upstream speed: 4 − 2 = 2 km/h
Downstream speed: 4 + 2 = 6 km/h
Let the distance to the point be D km.
Upstream time = D / 2 = 9 hours, so D = 2 × 9 = 18 km.
Downstream time = D / 6 = 18 / 6 = 3 hours.
Therefore the required downstream time is 3 hours.