A train crosses a platform — Aptitude Question
A train crosses a platform: A 200 m train crosses a 300 m platform in 25 seconds. What is the speed of the train? Answer and worked solution on CodeKairo.
- Topic: Time, Speed & Distance
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
A 200 m train crosses a 300 m platform in 25 seconds. What is the speed of the train?
Options
- 60 km/h
- 72 km/h
- 80 km/h
- 90 km/h
Show the answer and the worked solution
Correct answer: B. 72 km/h
Worked solution
- Distance covered = 200 + 300 = 500 m in 25 s, so speed = 20 m/s.
- 20 × 18/5 = 72 km/h.
Answer: 72 km/h.
The idea
Crossing an object of length L means covering (train length + L). For a person or a pole, L = 0.
Shortcut. 500 m in 25 s is 20 m/s, which is twice the 10 m/s = 36 km/h anchor: 72 km/h.
Common trap. 80 km/h — converting 20 m/s with a rounded factor of 4 instead of 3.6; 20 × 18/5 = 72 km/h.