In a proportional relationship, the constant of proportionality is the number you can multiply each value of x by to get the related value of y. You can use this idea to figure out whether a set of values is in a proportional relationship. Divide each value of y by the related value of x. Do you get the same number every time? In our ice cream example, $2 divided by 1 scoop equals 2. $4 divided by 2 scoops also equals 2. And $6 divided by 3 scoops…you get the picture! The relationship’s proportional, and the constant is 2.