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Here are some tips for Circle Circumference, which aligns with Texas state standards:

Circle Circumference


For a review of basic circle terms, please see Circle Area tips.

The circumference (C) of a circle is the distance around the circle.
r = radius
d = diameter
C = circumference
 
diameter = 2 × radius
d = 2 r
Circumference = 2 π × radius = π × diameter
C = 2 π r
C = π d


Example 1: Area answer in terms of π

Find the circumference in terms of π. Type "pi" in for π so that a correct answer would look like 7pi m Circumference:

Since we know the radius, use the circumference equation C = 2 π r.

C = 2 π r
  = 2 π (28 mi)
  = 56 π  mi
The answer is   Circumference:


Example 2: Area answer with π = 22/7

Find the area. Use 22/7 as an approximation for π. A correct answer would look like 14.5 cm.

Using the same problem as Example 1, we know that the circumference C

C = 56 π  mi
  =
56 ( )  mi
  =
856 ( )  mi
  = 176  mi
The answer is   Circumference:

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