Fill in the table and find the rule

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

36 girls

step-by-step explanation:

the 48 boys is 4 parts of the ratio

divide 48 by 4 to obtain one part of the ratio

= 12 ← 1 part of the ratio

3 parts = 3 × 12 = 36 ← number of girls