 A ratio is the relationship between two numbers. We use the colon to represent a ratio. In the gymnastics club, there are two boys for every three girls. There are 15 girls in the club. How many boys are there in the club? Using this table, can you see a pattern develop? There are multiples of two in the boys column and multiples of three in the girls column. Therefore, for every 15 girls, there are 10 boys. You can also conclude that the number of boys is two thirds the number of girls. And the number of girls is one and a half times the number of boys.