Multiple choice

Directions: Find the wrong number in the following number series. 11, 15, 23, 39, 71, 139, 263

  1. 263

  2. 139

  3. 71

  4. 39

  5. 15
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B Correct answer
Explanation

The pattern is: 11*2-7=15, 15*2-7=23, 23*2-7=39, 39*2-7=71, 71*2-7=135 (not 139), 135*2-7=263. The wrong number is 139.

AI explanation

The pattern follows the logic of multiplying the previous number by 2 and subtracting 7. Applying this, we get (11 x 2) - 7 = 15, (15 x 2) - 7 = 23, and (23 x 2) - 7 = 39. Continuing the pattern, (39 x 2) - 7 = 71 and the next term should be (71 x 2) - 7 = 135. Therefore, 139 is the wrong number in the series.

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