In previous lessons, students used gridded rectangles to relate area to multiplication. They also were introduced to the standard units of square inch, square centimeter, square foot, and square meter. In this lesson, students work with rectangles in which the squares are progressively less visible to encourage students to multiply the side lengths to find the area. This takes the form of partially tiled rectangles and rectangles with side lengths marked off in linear units. Students will connect the approaches they use and discuss multiplying side lengths to find area. When students use multiplication to find the areas of rectangles, they are using the structure of equal rows, or columns, and relating this to the operation of multiplication (MP7).

In this lesson, students see diagrams of rectangles that are described with standard units, such as square inches and square meters, but are not to scale. They will gain experience working with such diagrams throughout the unit. Students should understand that shapes and figures may not be the size indicated by the units, because drawing a picture can help us understand a situation even if we cannot draw the actual size.

How did students change their approach for finding area when they saw rectangles that were partially tiled or that showed only tick marks along two sides?