For a complete lesson on polygons, go to http://www.MathHelp.com - 1000+ online math lessons featuring a personal math teacher inside every lesson! In this lesson, students learn that a circle graph is a circular graph that uses different sized pie pieces to show how parts of a data set compare to a whole data set. Each pie piece represents a given percent of the entire circle, and all the pie pieces must add to 100%. Students are then asked to answer questions based on given circle graphs.