1, 9, 25, 49, ? — Number & Letter Series Aptitude Question
1, 9, 25, 49, ?: Find the next term: 1, 9, 25, 49, ? Answer and worked solution on CodeKairo.
- Topic: Number & Letter Series
- Section: Logical Reasoning
- Difficulty: Easy
- Time target: 40 seconds
Question
Find the next term:
1, 9, 25, 49, ?
Options
- 64
- 72
- 81
- 100
Show the answer and the worked solution
Correct answer: C. 81
Worked solution
- The terms are 1², 3², 5², 7².
- Next = 9² = 81.
Answer: 81.
The idea
When squares skip values, check whether the roots follow their own pattern — here the odd numbers.
Shortcut. The gaps 8, 16, 24 are multiples of 8, so the next gap is 32 and 49 + 32 = 81 — confirming the roots 1, 3, 5, 7, 9.
Common trap. 64 — taking the next square after 7², i.e. 8², and forgetting that the roots skip every even number.