A circle is a shape where all points are the same distance from the center of the circle. The radius (r) of a circle is the distance from the center of the circle to any point on the circle. The diameter (d) of a circle is the distance across the circle through the center.

Area (A) is the number of square units it takes to cover the surface of a shape. Area is expressed in square units such as cm², in², or ft².

In the circle diagram below, the

shaded part

of the circle is the area.

r = radius d = diameter   diameter = 2 × radius d = 2 r Area = π × radius 2 A = π r 2

Example 1: Area answer in terms of π

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

The diameter of the circle is 3 yd. To calculate the area of the circle, we will first find the radius of the circle.

d = 2 r

r = = = 1.5 yd

Now we are ready to calculate the area of the circle.

A	=	π r 2
	=	π (1.5 yd)2
	=	π (2.25 yd2)
	=	2.25π yd2

The answer is   Area:

Example 2: Area answer with π = 3.14

Find the area. Use 3.14 as an approximation for π. A correct answer would look like 14.5 sq cm.

Using the same problem as Example 1, we know that the area A

A	=	2.25π yd2
	=	2.25(3.14) yd2
	=	7.065 yd2

The answer is   Area: