1. Area of Circles Today you will learn to find the area of circles.

2. Review diameter (d) radius (r) d=2r

3. Area of Circles The area of a circle is equal to the product of pi () and the square of it’s radius. A=r2

4. Area of Circles Find the area of the circle below. A=r2 A≈ 3.14(3)2 A≈ 3.14(9) A≈ 28.26 m2 3 m

5. Area of Circles Your turn: Find the area of a circle with radius 10 cm. Remember to show all of your work!

6. Area of Circles A=r2 A≈ 3.14(10)2 A≈ 3.14(100) A≈ 314 cm2

7. Area of Circles Find the area of a circle with a diameter of 10 m. A=r2 You must find the radius before you can find the area!

8. Area of Circles Find the radius by dividing the diameter by 2. d=10 m r=d÷2 r=10÷2 r= 5 m

9. Area of Circles Now that you have found the radius of the circle, you can find the area. A=r2 A ≈ 3.14(5)2 A ≈ 3.14(25) A ≈ 78.5 m2

10. Area of Circles Now it’s your turn to try one! Find the area of a circle with diameter 40 mm.

11. Area of Circles A=r2 A ≈ 3.14(20)2 A ≈ 3.14(400) A ≈ 1256 mm2

12. Area of Circles Homework: Practice Workbook Lesson 11-6 Don’t forget to show all of your work!