Combining A : B and B : C — Aptitude Question
Combining A : B and B : C: If A : B = 2 : 3 and B : C = 4 : 5, what is A : B : C? Answer and worked solution on CodeKairo.
- Topic: Ratio & Proportion
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
If A : B = 2 : 3 and B : C = 4 : 5, what is A : B : C?
Options
- 6 : 9 : 10
- 4 : 6 : 5
- 2 : 3 : 5
- 8 : 12 : 15
Show the answer and the worked solution
Correct answer: D. 8 : 12 : 15
Worked solution
- Make B equal in both: A : B = 2 : 3 = 8 : 12 and B : C = 4 : 5 = 12 : 15.
- So A : B : C = 8 : 12 : 15.
Answer: 8 : 12 : 15.
The idea
To join two ratios that share a term, scale each so the shared term matches (usually its LCM). The same trick chains three or more ratios.
Shortcut. Cross-multiply: A : B : C = (2 × 4) : (3 × 4) : (3 × 5) = 8 : 12 : 15.
Common trap. 2 : 3 : 5 — writing the ratios side by side without making B's two values (3 and 4) equal.