1. Calculating Circumference

2. Circumference Defined
Circumference is the boundary of a circle or the length of this boundary.

3. Copy the following chart in your Notes:
Circumference
(cm)
Diameter
Circumference ÷ Diameter (cm)
(to two decimal places)
Radius
Circumference ÷ radius (cm)
Circle 1
Circle 2
Circle 3
Draw 3 circles of random size on the chart paper provided.
Measure the circumference of each (using string) and record
Measure the diameter* of each and record.
Complete the last 3 columns of the table.

4. Do you Notice Any Patterns?

5. Do you Notice Any Patterns?
Circumference ÷ diameter was always really really close to 3. This shows that approximately 3 diameters will equal the circumference

6. Online Activity
Google Search Ontario Education Resource Bank Search activity # ELO Click content, click next, click “Pi, Please with a side of a baseball” (this is your activity) The next slide will let you know what to do as you work through the learning experience

7. Pi Please, with a Side of Baseball
Record the diameter and circumference of each of the 3 objects (the puck, the golf ball and the pop can)
What is the relationships between diameter and circumference?
Write the symbol for pi, the numerical value of pi, and a definition of pi
Copy and complete question 5

8. Reflection Questions:
Do you notice any patterns?
How would you calculate the circumference of a circle if you knew only its radius?
If you knew the circumference of a circle, how would you estimate its diameter?
Why would you use a formula to determine the circumference of a circle, rather than measuring the circumference?

10. Pi (π)
Pi (π) is the ratio of the circumference to the diameter or the number of times the diameter of a circle divides the circumference. Its value is … or about 3.14, rounded to two decimal places. The formula for the circumference (C) of a circle with diameter (d) is C = πd The formula for the circumference of a circle with radius (r) is C = 2 πr