22, 21, 23, 22, 24, 23, ? — Aptitude Question
22, 21, 23, 22, 24, 23, ?: Find the next term: 22, 21, 23, 22, 24, 23, ? Answer and worked solution on CodeKairo.
- Topic: Number & Letter Series
- Section: Logical Reasoning
- Difficulty: Medium
- Time target: 75 seconds
Question
Find the next term:
22, 21, 23, 22, 24, 23, ?
Options
- 22
- 24
- 25
- 26
Show the answer and the worked solution
Correct answer: C. 25
Worked solution
- Odd positions (1st, 3rd, 5th): 22, 23, 24 — rising by 1.
- Even positions (2nd, 4th, 6th): 21, 22, 23 — also rising by 1.
- The seventh term is in the odd series, so it is 24 + 1 = 25.
Answer: 25.
The idea
When the differences alternate in sign, split the series by position and solve each half independently.
Shortcut. The steps run − 1, + 2, − 1, + 2, − 1, so the seventh step is + 2 and 23 + 2 = 25.
Common trap. 22 — applying − 1 again (23 − 1) after losing track of the alternation; the − 1 was just used, so + 2 comes next.