Parallelograms same base and same height

As you drag F, you create a family of parallelograms with the same base and the same height.
What can you say about the areas of parallelograms with the same base and the same height? Give a convincing argument that two parallelograms with the same base and the same height have the same area. [br]To change the base of the parallelogram, drag E.

Information: Parallelograms same base and same height