Area of circles
The area of any shape is the number of square units inside that shape. In the figure to the left, the square has an area of 36 square units, because there are 36 units inside the square. If each unit square in the circle were counted (including all the partial squares), there would be 28.26 unit squares inside the circle, so the area of this circle would be 28.26 square units. However, it is easier to use the following formula:
$A=\pi~r^2$ also known as $A=\pi~\cdot~r\cdot~r$
where A represents the area, and r is the radius of the circle.
| Finding area using π = 22/7 | Finding area using π = 3.14 |
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In terms of π.
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Duane Habecker, Created with GeoGebra
Self-check
Q1: What is the area of a circle with a radius of 10cm? (Use π = 3.14) [show answer]
Q2: What is the area of a circle with a radius of 7cm? (Use π = 3 1/7) [show answer]
Q3: What is the area of a circle with a radius of 3cm in terms of π? [show answer]
