Late at both speeds — Aptitude Question
Late at both speeds: A boy walking at 5 km/h reaches school 6 minutes late; walking at 6 km/h he is 2 minutes late. Answer and worked solution on CodeKairo.
- Topic: Time, Speed & Distance
- Section: Quantitative Aptitude
- Difficulty: Hard
- Time target: 120 seconds
Question
A boy walking at 5 km/h reaches school 6 minutes late; walking at 6 km/h he is 2 minutes late. How far is the school?
Options
- 1 km
- 1.5 km
- 2 km
- 2.5 km
Show the answer and the worked solution
Correct answer: C. 2 km
Worked solution
- Difference in time = 6 − 2 = 4 min = 1/15 hour.
- d/5 − d/6 = 1/15 → d(6 − 5)/30 = 1/15 → d/30 = 1/15.
- d = 2 km.
Answer: 2 km.
The idea
When both cases are late, subtract the lateness figures rather than adding them. Only one is early would mean adding.
Shortcut. Distance = (product of speeds ÷ difference of speeds) × time gap = (30 ÷ 1) × 4/60 h = 2 km.
Common trap. 1 km — using the 2 minutes late as the whole time gap (1 km takes 12 min against 10 min); the gap between the trips is 6 − 2 = 4 minutes.