1. Circles – They make the world go ‘round! (Circumference and Area)

2. Partner Vocabulary NotesPartner Vocabulary Notes  Share a copy of Buckle Down, Page 163-164  Complete foldable with vocabulary word, definition and picture.  10 minutes

3. “Parts of a Circle” Organizer“Parts of a Circle” Organizer  Create a class poster with all parts of the circle labeled. (see next slides)

4. DIAMETER DIAMETER is the distance through the CENTER of the circle. It is twice as large as the radius. d =diameter r= radius

5. Radius Radius is ½ as large as the diameter. R=1/2d

6. Parts of a Circle…Parts of a Circle…

7. Circumference Circumference is the distance around the circle. To find the circumference of a circle, you have to know the diameter or radius.

8. PI Pi is… the ratio of the circumference to the diameter.

9. The Area and Circumference of a CircleThe Area and Circumference of a Circle Diameter radius The circumference of a circle is the distance around the outside The area of a circle is the space inside it The circumference is found using the formula: C=πd or C= 2rπ (since d=2r) The area is found using the formula A= π r 2

10.  BEFORE WE BEGIN FINDING CIRCUMFERENCE AND AREA, YOU MUST REMEMBER THIS…  For every problem, you must show:  The Formula  The Substitutions  Final Answer  Labeling

11. The diameter of the quarter is 5.5cm. What is the circumference? What is the area?

12. AND THE ANSWER IS…..AND THE ANSWER IS….. approx 17.27 cm circumference approx. 23.74625 cm 2 Area

13. Why “APPROXIMATELY”?

14. The diameter of the circle is 8cm. What is the circumference? What is the area?

15. AND THE ANSWER IS…..AND THE ANSWER IS….. approx. 25.12 cm circumference approx. 50.24 cm 2 Area

16. The radius of the circle is 2cm. What is the circumference? What is the area?

17. AND THE ANSWER IS…..AND THE ANSWER IS….. approx. 12.56 cm circumference approx. 12.56cm 2 Area

18. A pizza place has an 8” diameter, 12” diameter, and a 16” diameter pizza. What is the area and circumference of those pizzas?

19. AND THE ANSWERS ARE (approximately)…..AND THE ANSWERS ARE (approximately)….. 8” Pizza: circumference: 25.12” area: 50.24 in 2 12” Pizza: circumference: 37.68” area: 113.04 in 2 16” Pizza: circumference: 50.24” area: 200.96 in 2

20. The area of a circle is 78.5 square meters. What is the radius?

21. AND THE ANSWER IS…..AND THE ANSWER IS….. Radius = 5 meters approximately

22. The circumference of a circle is 15.7 centimeters. What is the diameter?

23. AND THE ANSWER IS…..AND THE ANSWER IS….. Diameter = 5 cm approximately

24. Independent PracticeIndependent Practice  Buckle Down  Page 165-166  All problems  Homework if not complete

25. Using Circumference Formula and Area of a Parallelogram for Area of a Circle  Buckle Down  Page 164  Use Paper Plates or segmented circle to demonstrate

26. If time…If time…  Sir Cumference and the Round Table