Twenty years older — Problems on Ages Aptitude Question
Twenty years older: A is 20 years older than B. In 5 years A will be twice as old as B. What is B's present age? Answer and worked solution on CodeKairo.
- Topic: Problems on Ages
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 60 seconds
Question
A is 20 years older than B. In 5 years A will be twice as old as B. What is B's present age?
Options
- 10
- 15
- 20
- 25
Show the answer and the worked solution
Correct answer: B. 15
Worked solution
- b + 25 = 2(b + 5) = 2b + 10 → b = 15.
- Check: in 5 years, 40 and 20. ✓
Answer: 15.
The idea
One equation, one unknown, once the fixed difference is used. Expand the bracket before collecting terms.
Shortcut. When A is twice B, the gap equals B's age at that moment. The gap is 20, so B is 20 in five years and 15 now.
Common trap. 20 is B's age five years from now — the gap-equals-age step done right, but the five years never taken off.