Common Terms For Calculating Area
Question
There are four geometric objects that we commonly want to know the size of:
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Common Terms For Calculating Area

Hi, my name is Bassem Saad. I'm an associate math instructor and a Ph.D. candidate, and I'm here today for About.com to define common terms when calculating area.

Area is a way of understanding the size of an object. There are four geometric objects that we commonly want to know the size of -- that is a rectangle, a parallelogram, a triangle and a circle. We have a formula for each of their areas, based on measurements of certain edges or lengths.
Terms for Calculating Area of Rectangles

Ok, so the area of a rectangle is the base times height. The base is just one edge of the rectangle and the height will be just one edge of the rectangle because the edges are perpendicular.
Terms for Calculating Area of a Parallelogram

The same is true for a parallelogram: here we have the base of the parallelogram, which is just one of the edges of the parallelogram, and the height. Note that the height is not the other edge -- the perpendicular edge -- it's actually a perpendicular line from the base to the highest point on the parallelogram.
Terms for Calculating Area of a Triangle

The same is true for the triangle, but the triangle is one half times the base, times height. So again, the base is just one edge of the triangle and the height is a perpendicular distance from the base to the highest point on the triangle.
Terms for Calculating Area of a Circle

There you have the circle is just pi times the radius squared. The radius is r and it's any edge that starts from the center of the circle and goes out to the edge of the circle.
Units of Measurement for Calculating Area

So we measure a length, say with a ruler, we may use different units: centimeters, meters, inches, or feet. When calculating the area, we have a corresponding set of units: Centimeters corresponds to centimeters squared for area; length of meters corresponds to meters squared for area; inches corresponds to inches squared for area; and length in feet corresponds to feet squared in area.
Examples of Measurement Units for Calculating Area

To see how this works, let's look at a couple of examples. Say we had a rectangle with the base measured to be one foot and the height measure to be two feet. The area will be one foot, times two feet, resulting in two feet squared.

So for a circle, we could measure the radius to be one foot. So the area of a circle is pi, one foot squared. So that would just be pi feet squared, which is approximately equal to 3.14 feet squared. So now we know some common terms when calculating area.