Multiple choice general knowledge math & puzzles

Look at this series: 21, 9, 21, 11, 21, 13, 21, ... What number should come next?

  1. 14

  2. 15

  3. 21

  4. 23
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The odd positions (1st, 3rd, 5th, 7th) are all 21. The even positions show 9, 11, 13, which increase by 2 each time. The next number is at position 8 (even), so it follows 13+2=15. Option A (14) would break the +2 pattern, and option C (21) is at the wrong position.

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