6, 12, 21, 33, ? — Number & Letter Series Aptitude Question
6, 12, 21, 33, ?: Find the next term: 6, 12, 21, 33, ? Answer and worked solution on CodeKairo.
- Topic: Number & Letter Series
- Section: Logical Reasoning
- Difficulty: Easy
- Time target: 45 seconds
Question
Find the next term:
6, 12, 21, 33, ?
Options
- 45
- 48
- 51
- 54
Show the answer and the worked solution
Correct answer: B. 48
Worked solution
- Differences: 6, 9, 12.
- Next = 33 + 15 = 48.
Answer: 48.
The idea
Three differences are enough to establish an arithmetic pattern. Extend it by one step and add.
Shortcut. Divide by 3: 2, 4, 7, 11 has gaps 2, 3, 4, so its next term is 16 and the answer is 3 × 16 = 48.
Common trap. 45 — adding the last gap, 12, again (33 + 12); the gaps rise by 3, so the next is 15.