1. Circles
Circles are EVERYWHERE.

2. VOCABULARY
Diameter
Radius
Circumference Pi

3. DIAMETER Diameter is the distance through the middle of the circle.
It is twice as large as the radius.
d =diameter
r= radius

4. Radius Radius is ½ as large as the diameter. R=1/2d
The radius is used in many circle formulas

5. PI IS NOT :
A whole pie
A slice of pie

6. PI Pi is the ratio of the circumference to the diameter.
This is the symbol for pi p

7. The diameter of the quarter is 5.5cm.
What is the circumference?

8. AND THE ANSWER IS…..
17.27 cm

9. Circumference Circumference is the distance around the circle.
To find the circumference of a circle
You have to know the diameter or radius.

10. Radius = 4cm
Circumference = 2 X R X π
Circumference= 2 X 4 X 3.14
C= cm

11. Diameter = 10cm
C= π x D
C= 3.14 x 10
C= 31.4 cm

12. WHAT IS THE DIAMETER?
Radius is 6 inches
Diameter is 12 inches

13. LET’S PRACTICE
D= 24 INCHES
R= 12 inches