1. Measurement π Discovering Pi
Objective: (D5) To demonstrate an understanding of the relationships between diameter, radii and circumference of a circle and use the relationships to solve problems.

2. Discovering Pi
Open your document “WS - Discovering Pi” and review the relationship between the diameter and radius of a circle. r
d = 2 r
r = ½ d d

3. Circumference, represented by (C)
Measures of a Circle
Circumference, represented by (C)
Definition:
The distance around a circle (a type of perimeter) or the outside of the circle itself
Circumference (C)

4. Discovering Pi
Gather your circular objects you used to complete Part I of the activity.
Using a string or another method, measure the Circumference (C) of each circle as accurately as you can.
Enter these values into the table. d
Circumference

5. Discovering Pi
Find the ratio of the circumference (C) and the diameter (d) [C ÷ d] for each circle. Enter this into the table.
What do you notice about this ratio? d
Circumference

6. Area of a Circle
The ancient Greeks recognized that the circumference (C) of a circle was directly related to it’s radius (r) and diameter (d) by a fixed number.
They called this number π (pi).
It is approximately equal to 3.14.
Pi is non-terminating and non-repeating. C r d
C = π d

7. π to 1001 places

8. Remembering Pi
May I
Have A
Large
Container Of
Coffee 3 1 4 5 9 2 6

9. Estimating the circumference of each circle.
Area of a Circle
Estimating the circumference of each circle.
To estimate C, we can use π=~3

10. Area of a Circle Estimate the circumference of each circle. 2.5 cm

11. Area of a Circle
Now, use the formula C = π d to calculate the Circumference of each circle. Compare to your estimate.
2.5 cm
3.3 cm
π = 3.14

12. Assignment
Complete your assignment by answering the Assessment Questions 1-5 on the document “Discovering Pi”.
Place in “Discovering Pi” folder in the Student Drop Box when completed.