GRE Geometry - Parallelograms

A parallelogram is a four-sided figure, just like a rectangle or a square. However, unlike a square, all sides do not have to be of equal length, and unlike a square or a rectangle, the angles that are formed by the sides of the parallelogram do not have to be 90 degrees. Here are a few examples of parallelograms:

The only facts that you have to remember about parallelograms is that the area is the same as a rectangle, base times height, and that in order for a shape to be a parallelogram, opposite sides must be of equal length and angles opposite of each other are the same measure.