This document discusses how to calculate the cross-sectional area of a prism. It defines that a prism has two congruent polygon bases and three faces that are parallelograms. It explains that the cross-sectional area of a prism is the area of its base. The document then demonstrates how to calculate the area of two specific prisms by breaking them into triangles and rectangles and summing the individual areas. It concludes that the cross-sectional area of any prism is equal to the area of its base.