Emilie draws a circle with a diameter of 10 inches. Ethan draws a circle with a diameter that is half as long as the diameter of Emilie’s circle. How will the circumference of Ethan’s circle compare with the circumference of Emilie’s circle?
C=πr^2 Emilie d=10 so r=5 Ethan d=10/2=5 (half as long) r=2.5 Emilie c=π(5)^2=25π Ethan c=π(2.5)^2=6.25π 6.25 is a fourth of 25 so the circumference of Ethan’s circle is a fourth of the circumference of Emily’s circle.
