The document discusses how to calculate the area of circles. It reviews that the diameter (d) is equal to twice the radius (r) and that the area (A) of a circle is equal to pi (π) multiplied by the radius squared. Examples are provided of calculating the area of circles given the radius or diameter. Readers are prompted to practice calculating areas of circles on their own.

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

2. Reviewdiameter (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 CirclesFind the area of the circle below.A=r2 A≈ 3.14(3)2A≈ 3.14(9) A≈ 28.26 m23 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 CirclesA=r2 A≈ 3.14(10)2 A≈ 3.14(100) A≈ 314 cm2

7. Area of CirclesFind the area of a circle with a diameter of 10 m.A=r2You must find the radius before you can find the area!

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

9. Area of CirclesNow 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=r2A ≈ 3.14(20)2 A ≈ 3.14(400) A ≈ 1256 mm2

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