Surface Area
The figure shows a plane shape of a box
The box has sides 3x, x, and x
The surface area of the box is the sum of 6 rectangles: four of them have dimensions 3x by x. Two of them have dimensions x by x.
First, we compute the area of the rectangle of 3x by x:
Now, we compute the area of the rectangle (square really) of x by x:
As mentioned, there are 4 rectangles of area A1 and 2 squares of area A2, thus the total surface area is:
Since x= 6 in, the surface area of the geometric shape is