# Proportional Relationships and Slope

A constant difference refers to an equal amount that is being added or subtracted to two variables. In the cake Ms. Shafer is talking about, for every rise in height of 6 inches, the next tier of the cake is 1 inch over. This vertical rise of 6 inches and horizontal run of 1 inch is the constant difference. | Here is how the line would look if the top cake layer was a four-inch diameter cake, leaving a run of 2 inches. Notice how this makes the line, or the cake, tilt. |