Multiple choice

Find the wrong number in the series from the given alternative. 121, 143, 165, 186, 209, 231

  1. 121

  2. 143

  3. 186

  4. 165
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C Correct answer
Explanation

The pattern is +22, +22, +21, +23, +22. The differences should all be 22: 121+22=143, 143+22=165, 165+22=187 (not 186), 187+22=209, 209+22=231. The number 186 is one less than expected.

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