The image to the right shows the formulas for perimeter and area of two-dimensional shapes! 

Perimeter is the distance around the outside edge of the shape. 

Area is the amount of space inside of a shape. 

Key:   d=distance, r=radius, b=base, h=height, l=length, w=width, s=side, a=area, p=perimeter

While we have easy access to these formulas for surface area and volume, it is important to know WHY these formulas work. Consider the relation to other shapes and figures.

Triangles are relative to pyramids. 

Squares/rectangles are relative to cubes and prisms. 

Circles are relative to cones, spheres, and hemispheres. 

Key:   r=radius, b=base, h=height, l=length, w=width, sa=surface area, v=volume