Solving a proportion — Ratio & Proportion Aptitude Question
Solving a proportion: If 0.75 : x ∷ 5 : 8, what is the value of x? Answer and worked solution on CodeKairo.
- Topic: Ratio & Proportion
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
If 0.75 : x ∷ 5 : 8, what is the value of x?
Options
- 1.12
- 1.2
- 1.25
- 1.30
Show the answer and the worked solution
Correct answer: B. 1.2
Worked solution
- 0.75 × 8 = 5x → 6 = 5x.
- x = 1.2.
Answer: 1.2.
The idea
In a : b ∷ c : d the product of the extremes equals the product of the means. Cross-multiplying is the whole of it.
Shortcut. From 5 to 8 is × 1.6, so x = 0.75 × 1.6 = 1.2.
Common trap. "1.25" — the familiar partner of 0.75, but 0.75 : 1.25 = 3 : 5 = 0.6, just short of 5 : 8 = 0.625.