Question

Fill in the table and find the rule

Answer 1

It add by the number in the first column.
1 + 1 = 1
2+1=3
3+2=5
5+4=9

Answer 2

The table shows a relation where the first is sum by other number to obtain the second colum.

So, 1 + 0 = 1, the first row.

2 + 1 = 3

3 + 2 = 5

As you can see, the increasing number is the added part, and increases by one, that's the rule.

Then,

4 + 3 = 7

15 + 4 = 19

Therefore, the complete table is

1 1

2 3

3 5

4 7

15 19