11, 13, 17, 19, 23, ? — Aptitude Question
11, 13, 17, 19, 23, ?: Find the next term: 11, 13, 17, 19, 23, ? Answer and worked solution on CodeKairo.
- Topic: Number & Letter Series
- Section: Logical Reasoning
- Difficulty: Easy
- Time target: 40 seconds
Question
Find the next term:
11, 13, 17, 19, 23, ?
Options
- 25
- 27
- 29
- 31
Show the answer and the worked solution
Correct answer: C. 29
Worked solution
- The terms are consecutive primes.
- After 23 comes 29 (25 = 5² and 27 = 3³ are not prime).
Answer: 29.
The idea
Know the primes to at least 50. The composite traps 25 and 27 are always among the options.
Shortcut. Test the options in order above 23: 25 = 5² and 27 = 3³ fail, so the next prime is 29 — 31 is prime too but comes later.
Common trap. 25 — continuing the gap pattern 2, 4, 2, 4 with another 2 (23 + 2); 25 = 5² is not prime, and the next prime is 29.