Surface Area of a Cube
A cube has 6 faces or surfaces, all of them have the same size and therefore, the same area.
The surface area of one of the faces is the area of a square of side length 9 ft:
[tex]A=(9\text{ ft})^2=81\text{ }ft^2[/tex]
The total surface area is 6 times this area, thus:
[tex]\begin{gathered} SA=6\cdot81\text{ }ft^2 \\ SA=486\text{ }ft^2 \end{gathered}[/tex]
