Giselle will combine blue paint, green paint, and white paint in the ratio $3:2:4$, respectively. If she uses $12$ quarts of white paint, how many quarts of green paint should she use?
To do that, I can use the fact that the ratio of white paint to green paint is $4:2$, which means that for every $4$ quarts of white paint, there are $2$ quarts of green paint. So I can divide the given amount of white paint by $4$ to get the number of groups of $4$ quarts, and then multiply that by $2$ to get the number of quarts of green paint. That is, the number of quarts of green paint is $\frac{12}{4} \times 2 = 3 \times 2 = 6$. 