Find the missing number in the series: 3, 7, 15, 31, 63, ?
Find the missing number in the series: 3, 7, 15, 31, 63, ?
Each term is obtained by doubling the previous term and adding 1: 3x2+1=7, 7x2+1=15, 15x2+1=31, 31x2+1=63, 63x2+1=127. The missing number is 127.
Re-check your working by substituting the answer back into the original question.