Adding 7 to both — Ratio & Proportion Aptitude Question
Adding 7 to both: Two numbers are in the ratio 1 : 2. If 7 is added to each, the ratio becomes 3 : 5. Answer and worked solution on CodeKairo.
- Topic: Ratio & Proportion
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 75 seconds
Question
Two numbers are in the ratio 1 : 2. If 7 is added to each, the ratio becomes 3 : 5. What is the larger number?
Options
- 14
- 21
- 28
- 35
Show the answer and the worked solution
Correct answer: C. 28
Worked solution
- (x + 7)/(2x + 7) = 3/5 → 5x + 35 = 6x + 21 → x = 14.
- The numbers are 14 and 28, so the larger is 28.
Answer: 28.
The idea
The same pattern as before. Read the question carefully at the end — it asks for the larger number, and 14 is offered for those who stop at x.
Shortcut. Test the options as the larger number: 28 means 14 and 28, and adding 7 gives 21 : 35 = 3 : 5 exactly.
Common trap. "14" — solving x = 14 and stopping; x is the smaller number, and the question asks for the larger, 2x.