1. Warm-Up Find the area: 1.2. 3. 4. 7 20 13 22 18

2. Circumference and Area Circles

3. Vocabulary Circumference: The distance around a circle. Measured in units of length – feet, cm, inches. Area: The amount of surface covered by a figure. Measured in square units. Radius: The distance from the center of a circle to any point on the circle. (Half of the diameter.) Diameter: The distance across a circle through its center.

4. Formulas

5. Example 1 Find the approximate circumference and the area of the circular window shown: C = (3.14)(18) C = 56.52 inches A = (3.14)(9) 2 A = 254.34 inches 2 18 in

6. Example 2 The area of the circle is 600 ft 2. Find the diameter of the circle: Use 3.14 for Π. Round answer to the nearest hundredth. 600 = (3.14)r 2 d = 27.64 ft 3.14 3.14 191.08280254 = r 2 r = 13.82 ft

7. Area Formulas