Boat and stream from two speeds — Aptitude Question
Boat and stream from two speeds: A boat goes downstream at 16 km/h and upstream at 10 km/h. What is the speed of… Answer and worked solution on CodeKairo.
- Topic: Time, Speed & Distance
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 50 seconds
Question
A boat goes downstream at 16 km/h and upstream at 10 km/h. What is the speed of the boat in still water and of the stream?
Options
- 12 and 4 km/h
- 13 and 3 km/h
- 14 and 2 km/h
- 15 and 1 km/h
Show the answer and the worked solution
Correct answer: B. 13 and 3 km/h
Worked solution
- Boat = (16 + 10)/2 = 13 km/h.
- Stream = (16 − 10)/2 = 3 km/h.
Answer: 13 and 3 km/h.
The idea
Boat = (down + up)/2 and stream = (down − up)/2. These two formulas answer most boat questions immediately.
Shortcut. Every option adds to 16, so check the difference instead: boat − stream must be the upstream 10, and only 13 − 3 = 10.
Common trap. 12 and 4 km/h — it adds to the downstream 16 like every option, but 12 − 4 = 8, not the upstream 10.