30% exceeds 20% by 18 — Percentages Aptitude Question
30% exceeds 20% by 18: 30% of a number exceeds 20% of it by 18. What is the number? Answer and worked solution on CodeKairo.
- Topic: Percentages
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 40 seconds
Question
30% of a number exceeds 20% of it by 18. What is the number?
Options
- 120
- 150
- 180
- 200
Show the answer and the worked solution
Correct answer: C. 180
Worked solution
- 30% − 20% = 10% of the number.
- 0.10N = 18 → N = 180.
Answer: 180.
The idea
Subtract the percentages first, then solve one equation. Setting up 0.3N − 0.2N = 18 and simplifying is the same thing done more slowly.
Shortcut. Test the options: only 180 has a tenth of 18; 30% of 180 is 54 and 20% is 36, and 54 − 36 = 18.
Common trap. 200 — the tempting round figure, but its 30% and 20% (60 and 40) differ by 20, not 18.