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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