Multiple choice

Find the missing number in the following number series: $15, 31, ?, 127, 255, 511$

  1. 62

  2. 65

  3. 66

  4. 69

  5. 63

Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Pattern: each term = previous term × 2 + 1. 15 × 2 + 1 = 31, 31 × 2 + 1 = 63, 63 × 2 + 1 = 127, 127 × 2 + 1 = 255, 255 × 2 + 1 = 511. The missing number is 63.