How much space does a shape cover? This 3rd grade area with length and width worksheet shows three rectangles and one square, and each side carries its length. Your child finds the area of a rectangle by multiplying its length by its width. For the area of a square, both sides are the same, so the side is multiplied by itself. The second page is an answer key. It writes each step, from the two sides to the product, and ends with the area in square units such as square centimeters.