Multiple choice

Find out the wrong number in the following number series. 15 136 55 104 79 89

  1. 55

  2. 79

  3. 89

  4. 104

  5. 136
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The series alternates two interleaved sequences. Odd positions: 15, 55, 79 (difference: +40, +24). Even positions: 136, 104, 89 (difference: -32, -15). The pattern in differences shows 89 breaks the even sequence. Alternatively: 15+121=136, 136-81=55, 55+49=104, 104-25=79, 79+9=88 (not 89). 89 is wrong.

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