Triangular Numbers series.
The nth triangular number can be calculated by using the formula:
n(n+1)/2
The mathematical statement 31 plus 31 would have an answer of 62.
47
You double the number before it and add 1.
16 31-15=16 15-31=-16
The rule is 5, 10, 15 and so the next number will be 20+31 = 51
The mathematical statement 31 plus 21 equals 52 as a total.
31 - 15 = 16. There for 15 is 16 less than 31.
15/31
15 + 16 = 31
15+15+1=31
16 + 15 = 31
31-3d