Surface Area

The surface area of a two- or three-dimensional object measures the area of all the surfaces of the object. And area, as we know, is measured in square units, such as square inches, square feet, and so on.

An example of a two-dimensional object is a rectangular piece of paper, or a rectangular-shaped garden. In this case the surface area is simply the product of the object's length times the object's width. This can be seen by examining the area of this rectangle:

   An example of a three-dimensional object is a rectangular box. As you know, a box is
   constructed with four rectangular sides, a rectangular top, and a rectangular bottom.
   The surface area of a rectangular box, then, is the sum of the areas of its four sides plus
   the area of the top plus the area of the bottom

Sample Problem involving surface area: Find the surface area of an open box (this means it has no top!)
whose dimensions are 15" by 12" by 8".

           Solution:    Here we can substitute the x above with 15, the y above with 12", and the h above with
                                8".    Then, using the recipe for the surface area above, being mindful of the fact that this
                                box has no top, we get:

(15)(12) + 2(12)(8) + 2(15)(8) = 612 in.²