Three times as old, twelve years apart — Aptitude Question
Three times as old, twelve years apart: The ages of two brothers differ by 12 years and the elder is three times as… Answer and worked solution on CodeKairo.
- Topic: Problems on Ages
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 50 seconds
Question
The ages of two brothers differ by 12 years and the elder is three times as old as the younger. What is the elder brother's age?
Options
- 12
- 15
- 18
- 24
Show the answer and the worked solution
Correct answer: C. 18
Worked solution
- 3y − y = 2y = 12 → y = 6.
- Elder = 3 × 6 = 18.
Answer: 18.
The idea
When one age is a multiple of the other, the difference is (multiple − 1) times the smaller. One division finishes it.
Shortcut. The gap is two-thirds of the elder's age (3 parts − 1 part), so elder = 12 × 3/2 = 18. Check: 18 − 12 = 6 and 18 = 3 × 6.
Common trap. 24 comes from the 'twice as old' habit, where the gap equals the younger and the elder is double the gap; with 'three times' the gap is two parts, so 24 (younger 12) is only twice.