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: 50 seconds
Question
If A : B = 2 : 3 and B : C = 4 : 5, what is A : B : C?
Options
- 2 : 3 : 5
- 6 : 9 : 10
- 8 : 12 : 15
- 10 : 15 : 12
Show the answer and the worked solution
Correct answer: C. 8 : 12 : 15
Worked solution
- A : B = 2 : 3 = 8 : 12; B : C = 4 : 5 = 12 : 15.
- So A : B : C = 8 : 12 : 15.
Answer: 8 : 12 : 15.
The idea
Match the shared term by scaling each ratio to its LCM, then join. The same trick chains any number of ratios together.
Shortcut. Use the N-pattern: A = 2 × 4, B = 3 × 4, C = 3 × 5, which gives 8 : 12 : 15 in one line.
Common trap. "2 : 3 : 5" — gluing the two ratios together as written, though B is 3 in one and 4 in the other.