Multiple choice

Directions: In the following question, four numbers are given. Out of these, three are alike in a certain way but one is different. Choose the one which is different from the rest three.

  1. 7

  2. 15

  3. 31

  4. 57
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All other numbers can be expressed as a power of 2 minus one. Thus, 7 = 23 - 1, 15 = 24 - 1, 31 = 25 - 1.

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