Select the number from among the given options that can replace the question mark (?) in the following series.
1, 3, 7, 15, 31, 63, ?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 127.
Given series: 1, 3, 7, 15, 31, 63, ?
1 × 2 + 1 = 3; 3 × 2 + 1 = 7; 7 × 2 + 1 = 15; 15 × 2 + 1 = 31; 31 × 2 + 1 = 63; 63 × 2 + 1 = 127