Ratio of speeds to ratio of times — Aptitude Question
Ratio of speeds to ratio of times: The speeds of two cars are in the ratio 4 : 5. What is the ratio of the times… Answer and worked solution on CodeKairo.
- Topic: Time, Speed & Distance
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
The speeds of two cars are in the ratio 4 : 5. What is the ratio of the times they take to cover the same distance?
Options
- 4 : 5
- 5 : 4
- 16 : 25
- 25 : 16
Show the answer and the worked solution
Correct answer: B. 5 : 4
Worked solution
- For the same distance, time ∝ 1/speed.
- So the times are in the ratio 1/4 : 1/5 = 5 : 4.
Answer: 5 : 4.
The idea
Inverting a ratio is not the same as reversing the numbers in general, but for two terms it is. The faster car takes the smaller time.
Shortcut. For a fixed distance time ∝ 1/speed, so just flip the ratio; squared ratios such as 16 : 25 belong to areas, never to this inverse law.
Common trap. 4 : 5 — copying the speed ratio; the faster car (5) takes less time, so its share of the time ratio must be smaller.