Multiple choice

In the following number series a wrong number is given. Find out that wrong number. 7, 4, 5, 9, 20, 52

  1. 5

  2. 9

  3. 20

  4. 52

  5. No wrong number
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D Correct answer
Explanation

Pattern of differences: difference between consecutive terms is multiplied by 1, 2, 3, 4... 7→4 (diff -3), 4→5 (diff +1), 5→9 (diff +4), 9→20 (diff +11). Multipliers: 1/(-3), 1/1, 4/1=4, 11/4=2.75 - doesn't fit cleanly. Alternative: differences are -3, +1, +4, +11, +32. Next should be 52 + 32 = 84, not 52.

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