FORMULAS FOR MEASURING A CIRCLE
π = 3.14
2 x Radius = Diameter
1/2 x Diameter = Radius
Circumference = π x
Diameter
C = π D
Area = π x (Radius)2
A = π r2
Look at the circle above.
You should study this circle and remember these important formulas:
C (Circumference) π x D (Diameter)
or
C (Circumference) = 2 x π x r (Radius)
A (Area) π x r2 (Radius x Radius)
AREA is always expressed in square units.
After you have reviewed this page, try the problems on the next page.
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