In this interactive from APT, develop an understanding of circumference and the area of a circle and then practice these values with formulas. In the accompanying classroom activity, students review circumference and area of circles and then use the interactive. They use the formulas to solve area and circumference problems drawn from real-life contexts. To get the most from the activity, students should have some experience with the formulas for circumference and area of a circle. Students should also have exposure to some or all of the concepts reflected in the vocabulary list below.