Multiple choice

Find the wrong number in the given below series. 12, 30, 99, 408, 2050, 12348

  1. 12

  2. 30

  3. 2050

  4. 408

  5. 99
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pattern: ×1+18, ×2+9, ×3+8, ×4+7, ×5+6, ×6+5: 12×1+18=30 (match), 30×2+9=69 (not 99). Alternative: ×2+6, ×3+9, ×4+12, ×5+15, ×6+18. 12×2+6=30 (match), 30×3+9=99 (match), 99×4+12=408 (match), 408×5+15=2055 (but given 2050), 2055×6+18=12348 (match). So 2050 should be 2055 (408×5+15=2040+15=2055). 2050 is the wrong number.

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