Imagine a 3-dimensional shape like the one above, a cube, or a host of others: balls, boxes, cylinders. There are two ways to measure 3-dimensional shapes like these:

1) Surface Area: the surface area is the number of square units it takes to cover a 3-D shape- imagine wrapping paper. It's a 2-D measurement wrapped around a 3-D shape.

2) Volume: Volume, on the other handing, isn't a covering, it fills a 3-D shape. Like the water in a water bottle or the sand in a sandbox. Because volume completely fills a 3-D space, it's also 3-dimensional so it's measured in cubic units.

As usual, with GED Geometry these formulas show up on the GED formula sheet so all you have to do is choose the appropriate formula, substitute in the known values, then rely on your algebra skills to solve for the unknown variable.

Watch the Virtual GED Class video below for a complete explanation and tons of worked example problems.