Transcript Circles - kentbutler / FrontPage

Circles
Circles are EVERYWHERE.
VOCABULARY
Diameter
Radius
Circumference
Pi
DIAMETER
Diameter is the distance through the middle of the circle.
It is twice as large as the radius.
d =diameter
r= radius
Radius
• Radius is ½ as large as the
diameter.
• R=1/2d
• The radius is used in many
circle formulas
PI IS NOT :
• A whole pie
• A slice of pie
PI
• Pi is the ratio of
the
circumference
to the diameter.
This is the symbol for pi p
The diameter of the quarter is 5.5cm.
What is the circumference?
AND THE ANSWER IS…..
17.27
cm
Circumference
• Circumference is the
distance around the
circle.
To find the circumference of a circle
You have to know the diameter or radius.
Radius = 4cm
Circumference = 2 X R X π
Circumference= 2 X 4 X 3.14
C= 25.12 cm
Diameter = 10cm
C= π x D
C= 3.14 x 10
C= 31.4 cm
WHAT IS THE
DIAMETER?
Radius is 6 inches
Diameter is 12 inches
LET’S PRACTICE
D= 24 INCHES
R= 12 inches