Multiple choice

In the following number-series, one number is wrong. Find the wrong number: 5 8 20 42 124 246

  1. 8

  2. 20

  3. 42

  4. 124

  5. 5
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B Correct answer
Explanation

The pattern is: 2n - 2, then 2n + 4 alternately. 5*2 - 2 = 8, 8*2 + 4 = 20, 20*2 - 2 = 38, but we have 42. The correct number should be 38, making 20 the wrong term. Alternatively, if following from 8: 8*2 + 4 = 20, then 20*2 + 4 = 44 (but we have 42). The pattern breaks at 20.

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