1. Do Now:

2. Circumference

3. What is circumference? Circumference is the distance around a circle

4. To calculate the circumference… We use diameter to calculate circumference, but we need to multiply the diameter by something That is where pi comes in! Circumference = (Diameter)( π )

5. Pi! For every circle – –If you measure the circumference and the diameter and divide the circumference by the diameter, you will get pi.

6. Let’s see how close you can get to the actual value of pi!

7. Finding Circumference Formula: Circumference = (Diameter)( π ) Example: If a circle has a diameter of 3 meters, what is the circumference? Provide an exact answer. Circumference = (Diameter)( π ) Circumference = (3)( π ) Circumference = 3 π Exact Answer

8. Working Backwards If a circle has a circumference of 12 π meters, what is the radius? Circumference = (Diameter)( π ) 12 π = (Diameter)( π ) 12 = Diameter 6 = Radius

9. What if there is no pi? The circumference of a circle is 25.13 meters. Find the radius and round your answer to the nearest whole number. Circumference = (Diameter)( π ) 25.13 = (Diameter)( 3.14 ) 8.003 ≈ Diameter 4 ≈ Radius Approximate Answer