1. Student materials: Copy of Circle Investigation, Scissors, Centimeter Ruler, and Yarn
Circles

2. Circumference of Circles
10.3 Notes
Circumference of Circles
Determine the diameter if you don’t know it
Copy the equation (don’t just solve in your head)
Substitute the numbers for the variables
Solve

3. I can… Find the diameter of a circle Find the radius of a circle
Calculate the circumference of a circle
Self Assessment
5- I can do it without help & teach others.
4- I can do this with no help, but I don’t know if I can explain it.
3- I can do this with a little help.
2- I can do this with a lot of help!
1- I don’t have a clue.

4. Center

5. Radius

6. Radii

7. Diameter

8. Circumference

9. Chord

10. 2r = d Radius + Radius Diameter 2)d = r 2 X Radius = Diameter
Diameter ÷ 2 = Radius

11. A. 1 in
B. 3 in
3 in
D = ?
C. 6 in
D. 12 in

12. A. 3 in
B. 6 in
6 in
D = ?
C. 9 in
D. 12 in

13. A. 3 in
B. 6 in
6 in
R = ?
C. 9 in
D. 12 in

14. A. 1.5 in
B. 3 in
3 in
R = ?
C. 6 in
D. 12 in

15. Using the provided circle templates, you and your teammate(s) will:
Circle Investigation
Using the provided circle templates, you and your teammate(s) will:
Cut out circle templates
Measure the radius and diameter of each circle to the nearest tenth of a centimeter
Measure the circumference with yarn and then measure the yarn to the nearest tenth of a centimeter
Divide the circumference by the diameter
Fill in the table for each circle
Discuss and answer questions on the bottom of the worksheet

16. Investigation Discussion
How is the radius related to the diameter?
How are the radius and the circumference related?
How are the diameter and the circumference related?

17. Circumference How do you find the circumference of a circle?
is the symbol for the Greek letter Pi.

18. Pi is an irrational number.

19.
3.14

20. Circumference C = πd D = π)c Pi = π 3.14 = Pi
Diameter x 3.14 = Circumference
3.14 = Pi
D = π)c
Pi = π

21. C = πd
8 ft
25.12
2.512
24.32
24.82
3.14 = Pi

22. C = πd
15 cm
32.46
46.21
47.1
74.1
3.14 = Pi

23. C = πd
25 cm
75.83
57.8
5.78
78.5
3.14 = Pi

24. C = πd
10 m
62.8
6.28
31.4
3.14
3.14 = Pi

25. C = πd
15 m
4.71
47.1
92.4
94.2
3.14 = Pi

26. 40 yds
R = ? 20 40 60 80

27. 16 m
R = ? 4 8 16 32

28. 20 cm
D = ? 10 20 30 40

29. 16 ft
D = ? 8 16 32 48

30. I can… Find the diameter of a circle Find the radius of a circle
Calculate the circumference of a circle
Self Assessment
5- I can do it without help & teach others.
4- I can do this with no help, but I don’t know if I can explain it.
3- I can do this with a little help.
2- I can do this with a lot of help!
1- I don’t have a clue.

31. Circumference of Circles
10.3 Notes
Circumference of Circles
Determine the diameter if you don’t know it
Copy the equation (don’t just solve in your head)
Substitute the numbers for the variables
Solve