4, 7, 12, 19, 28, ? — Aptitude Question
4, 7, 12, 19, 28, ?: Find the next term: 4, 7, 12, 19, 28, ? Answer and worked solution on CodeKairo.
- Topic: Number & Letter Series
- Section: Logical Reasoning
- Difficulty: Easy
- Time target: 45 seconds
Question
Find the next term:
4, 7, 12, 19, 28, ?
Options
- 37
- 38
- 39
- 41
Show the answer and the worked solution
Correct answer: C. 39
Worked solution
- Differences: 3, 5, 7, 9, rising by 2.
- Next = 28 + 11 = 39.
Answer: 39.
The idea
The same odd-difference pattern, shifted. The terms are n² + 3.
Shortcut. Odd gaps flip the parity each step (4 even, 7 odd, 12 even, 19 odd, 28 even), so the blank is odd — ruling out 38 — and 39 − 3 = 36 is the only square fit.
Common trap. 37 — adding the last gap, 9, again (28 + 9); the gaps rise by 2, so the next is 11.