When you have finished this page, try the Area Quiz.
The area of a geometric plane figure such as a polygon is the measure of the number of square units the object or plane figure is made up of. To find the area of a polygon, you must figure how many square units would fit within that polygon. Thus the result is labeled as square units. There are different ways to find the area of a polygon.
One is to count the square units in a figure. In the polygon below one can see such an example.
Squares & Rectangles:
To find the area of a square and/or a rectangle, simply multiply the number of units in the length times the number of units in the width. For a square these are the same number as all four sides of a square are equal. The formula for the area of a rectangle would be:
Area = Length times the width
The area of a square would be:
Area = side times side
For this figure the area would be 12 times 12 or 144 square units.
Triangles:
The area of a triangle is 1/2 the length times the height of the triangle. Here are some illustrations:
|
Height
of 12 units
|
 |
| Base of 12 units |
For a right triangle, it is simple to see the base and height. In this case it would be one half of 12 times 12 which is 72.
This illustration show how a triangle is in reality half of a square or rectangle if one fills in the other half. It is easy to see how the formula for the area of the triangle relates to that of the rectangle or square.
The area of a circle equals the radius times itself times pi. Pi is a mathematical number equal to approximately 3.14 which is the actual number rounded. Since circles are curved, their area to not compute as evenly as squares and rectangles. In this case the area would be 5.5 times 5.5 times 3.14 square units.
