Catching up — Time, Speed & Distance Aptitude Question
Catching up: A thief runs at 10 km/h and a policeman 100 metres behind chases at 12 km/h. Answer and worked solution on CodeKairo.
- Topic: Time, Speed & Distance
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 75 seconds
Question
A thief runs at 10 km/h and a policeman 100 metres behind chases at 12 km/h. How long does the policeman take to catch him?
Options
- 2 min
- 3 min
- 4 min
- 5 min
Show the answer and the worked solution
Correct answer: B. 3 min
Worked solution
- Relative speed = 2 km/h.
- Gap = 100 m = 0.1 km.
- Time = 0.1 ÷ 2 = 0.05 h = 3 minutes.
Answer: 3 min.
The idea
Chasing uses the difference of speeds. Keep the gap and the speed in the same units before dividing, then convert the answer to minutes.
Shortcut. 2 km/h is 2,000 m in 60 minutes, i.e. 100 m every 3 minutes — the gap closes in 3 min.
Common trap. 5 min — reading 0.05 h (0.1 km ÷ 2 km/h) as 5 minutes; 0.05 of an hour is 0.05 × 60 = 3 minutes.