Multiple choice

In the following question, a number series is given with one term missing. Choose the correct alternative that will continue the same pattern and fill in the blank spaces. $3, 7, 15, 31, 63, (?)$

  1. $121$
  2. $122$
  3. $124$
  4. $127$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Looking at the number series: 3, 7, 15, 31, 63. The pattern is: multiply by 2 and add 1. 3×2+1=7, 7×2+1=15, 15×2+1=31, 31×2+1=63. Continuing: 63×2+1=127. Alternatively, each number is one less than a power of 2: 4-1=3, 8-1=7, 16-1=15, 32-1=31, 64-1=63, 128-1=127. The next number is 127 (option D).

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