Multiple choice

Which number is wrong in the given series? 3, 7, 7, 11, 9, 13, 13, 17, 15, 23

  1. 9

  2. 23

  3. 13

  4. 17
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The series has two alternating patterns. Odd positions (3, 7, 11, 15) increase by 4 each time. Even positions (7, 9, 13, 17) should also increase by 4, but 9 should be 11 (since 7+4=11, then 11+2=13, 13+4=17). The number 23 violates both patterns - it should be 19 at position 10.

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