7th Grade Section
WME@Kimpton Middle

Area of a Circle

A ParallelogramWhat is a circle? It is a curve on which all the points are at the same distance from the origin of the circle.

This distance is the radius of the circle. The diameter of a circle is two times the radius.

  1. Circumference of a circleThe circumference of a circle is always a constant multiple of its diameter. This is a fundamental truth in the universe. The Greek symbol π is used to represent this constant.

    To five decimal places π is approximately 3.14159.

    Thus, a circle with a radius 5 cm has a circumference approximately:  cm 

  2. Area of a circleThe area of a circle is the radius squared × π, or π r2.

    Thus, a circle with a radius 10 cm has an area approximately:
     cm2 



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