13, 35, 57, 79, 911, ? — Aptitude Question
13, 35, 57, 79, 911, ?: Find the next term: 13, 35, 57, 79, 911, ? Answer and worked solution on CodeKairo.
- Topic: Number & Letter Series
- Section: Logical Reasoning
- Difficulty: Hard
- Time target: 105 seconds
Question
Find the next term:
13, 35, 57, 79, 911, ?
Options
- 1,011
- 1,113
- 1,213
- 1,315
Show the answer and the worked solution
Correct answer: B. 1,113
Worked solution
- Each term is two consecutive odd numbers written side by side: 1|3, 3|5, 5|7, 7|9, 9|11.
- The next pair is 11 and 13, giving 1113.
Answer: 1,113.
The idea
When the arithmetic makes no sense, read the digits as a pattern rather than the value. Concatenation series are common in the harder papers.
Shortcut. Each term's second number starts the next (1|3 → 3|5 → … → 9|11), so the blank begins with 11 and adds the next odd number, 13: 1113.
Common trap. 1,315 — thinking the pairs do not overlap and starting after 11 with 13|15; each new pair repeats the previous pair's last number, so it is 11|13.