Circumference = ? (Animation)

[b][color=#1551b5]Let's try to find the circumference of a circle by wrapping diameters around it.[/color][/b][br][br][b][color=#c51414]Hit the "Start Animation!" button below and carefully observe what happens.[/color][/b][br][i][color=#0a971e](Be sure to answer the 2 questions that follow.)[/color][/i]

Information: Circumference = ? (Animation)