1. Math Circumference of Circles & Area of Circles

2. Vocabulary A circle is the set of all points in a plane that are the same distance from a given point, called the center. The circumference C is the distance around a circle. The radius r is the distance from the center to any point on a circle. The diameter d is the distance across a circle through its center.

3. Vocabulary The diameter of a circle is 2 times the radius, or d = 2r. An approximation for π is 3.14.

4. Circumference of a Circle The circumference C of a circle is equal to its diameter d times π, or 2 times its radius r times π. C = πd or C = 2πr

5. 1. Radius = 8 ft 2. Radius = 7 yd 3. Diameter = 21 ft 4. Diameter = 14 m 5 Calculate the circumference

6. Math Area of a Circle

7. The area A of a circle equals the product of π and the square of its radius. A = πr²

8. 1. Radius = 8 cm 2. Diameter = 17 cm 3. Diameter = 6.5 m 4. Radius = 9 in 8 Calculate the area

9. Find the radius of a circle that has an area of 42 square centimeters. Round to the nearest tenth. 9 CHALLENGE