1. Circumference
Definition: The distance around a circle. It’s a special word for perimeter. Picture:

2. Pi: 𝜋
Definition: The ratio between the circumference and diameter of an circle. Picture: ***Use the 𝜋 key on your calculator. If you do not have a 𝜋 key, then use 3.14.

3. Circumference Formulas
C= 𝝅𝒅 or C = 2𝝅𝒓
d = diameter
r = radius
C= circumference

4. Let’s Practice… Round all answers to nearest tenth (0.1)
If a circle has a radius of 5, what is it’s circumference?
If a circle has a diameter of 7, what is it’s circumference?
If a circle has a circumference of 12𝜋, what is the diameter?
If a circle has a circumference of 20𝜋, what is the radius?