B as a percentage of A — Percentages Aptitude Question
B as a percentage of A: If 90% of A = 30% of B and B = x% of A, what is the value of x? Answer and worked solution on CodeKairo.
- Topic: Percentages
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 50 seconds
Question
If 90% of A = 30% of B and B = x% of A, what is the value of x?
Options
- 100
- 200
- 300
- 400
Show the answer and the worked solution
Correct answer: C. 300
Worked solution
- 0.9A = 0.3B → B = 3A.
- B as a percentage of A = 300%, so x = 300.
Answer: 300.
The idea
A percentage above 100 is perfectly ordinary — it just means the quantity is larger than its base. Candidates who assume percentages must be under 100 pick 100 here.
Shortcut. B/A = 90/30 = 3 (the percentages swap sides), and three times a quantity is 300% of it.
Common trap. 200 — giving how much more B is than A (3A is 200% more than A) instead of B as a percentage of A.