What’s the next number? 12 21 23 32 34 43
The correct answer and explanation is:
The next number in the sequence 12, 21, 23, 32, 34, 43 is:
45
Explanation (300 words):
To find the next number in a sequence, we need to look for patterns. Let’s examine the numbers:
- 12
- 21
- 23
- 32
- 34
- 43
Observe that all numbers are two-digit numbers made by distinct digits. Let’s look more closely:
- 12 → 21 – Digits reversed.
- 21 → 23 – The tens digit stayed 2, ones digit increased from 1 to 3.
- 23 → 32 – Digits reversed.
- 32 → 34 – Tens digit stays 3, ones digit increases.
- 34 → 43 – Digits reversed.
This suggests a repeating pattern of reversing digits and then incrementing the last digit. In summary:
- Start with a number like 12
- Reverse it → 21
- Change the last digit while keeping the tens digit → 23
- Reverse it → 32
- Change the last digit → 34
- Reverse it → 43
Following this observed pattern:
- After 43, keep the tens digit (4), increase the ones digit from 3 to 5
- Result: 45
This continues the trend:
- Alternating between reversing and increasing the ones digit
- Digits are always increasing in value or being swapped
Thus, the correct answer is 45.
Pattern Recap:
- 12 → 21 (reverse)
- 21 → 23 (same tens, increase ones)
- 23 → 32 (reverse)
- 32 → 34 (same tens, increase ones)
- 34 → 43 (reverse)
- 43 → 45 (same tens, increase ones)
This systematic alternation between reversing and incrementing gives us a reliable method to determine the next number in the sequence.