Using a TI-73 or other similar graphing calculator middle school math majors investigate the linear relationship of equivalent proportions. After a brief introduction by the teacher, class members participate in a timed pair share activity using an included worksheet as their guide. They get independent practice by examining the proportional measures within a circle. Finally, they complete a homework assignment on the rate of change. For all of these, there is a worksheet provided. You can easily implement this lesson without the calculators as well.