Multiple choice

Find the wrong number in the following number series. 1527, 1185, 985, 865, 823, 817

  1. 985

  2. 865

  3. 823

  4. 817

  5. 1185
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The pattern is: subtract 21×1=21, 21×2=42, 21×4=84, 21×8=168, 21×16=336. Checking: 1527-200=1327 (not 1185, should be 1527-21×16=1527-336=1191). Working backwards from 817: if 823 came from 817+6=823, then 865 should come from 823+42=865 (correct), 985 from 865+84=949 (wrong! Should be 949, not 985). Therefore 985 is the wrong number.

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