Raising the speed to save time — Aptitude Question
Raising the speed to save time: A man covers a distance in 6 hours at 40 km/h. At what speed must he travel to… Answer and worked solution on CodeKairo.
- Topic: Time, Speed & Distance
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
A man covers a distance in 6 hours at 40 km/h. At what speed must he travel to cover it in 4 hours?
Options
- 50 km/h
- 55 km/h
- 60 km/h
- 65 km/h
Show the answer and the worked solution
Correct answer: C. 60 km/h
Worked solution
- Distance = 40 × 6 = 240 km.
- Required speed = 240 ÷ 4 = 60 km/h.
Answer: 60 km/h.
The idea
Speed and time are inversely proportional for a fixed distance: two-thirds the time needs three-halves the speed.
Shortcut. The 2 hours saved at 40 km/h are 80 km that must be spread over the 4 new hours: + 20 km/h, so 40 + 20 = 60 km/h.
Common trap. 55 km/h comes from reading a third less time as a third more speed: 40 × 4/3 ≈ 53.3 km/h, nearest option 55. Cutting the time to 2/3 needs the speed × 3/2, so 40 × 3/2 = 60 km/h.