In Module 4, Topic A, students begin to conceptualize area as the amount of two-dimensional surface that is contained within a plane figure. They come to understand that the space can be tiled with unit squares without gaps or overlaps (3.MD.5). They make predictions and explore which rectangles cover the most area when the side lengths differ (but the area is actually the same). Students may, for example, cut and fold rectangles to confirm predictions about whether a 1 by 12 rectangle covers more area than a 3 by 4 or a 2 by 6 rectangle. They reinforce their ideas by using inch and centimeter square manipulatives to tile the same rectangles and prove the areas are equal. Topic A provides students’ first experience with tiling, from which they learn to distinguish between length and area by placing a ruler with the same size units (inches or centimeters) next to a tiled array to discover that the number of tiles along a side corresponds to the length of the side (3.MD.6).
In Module 4, Topic B, students progress from using square tile manipulatives to drawing their own area models. Anticipating the final structure of an array, they complete rows and columns in figures such as the example shown at the right. Students connect their extensive work with rectangular arrays and multiplication to eventually discover the area formula for a rectangle, which is formally introduced in Grade 4 (3.MD.7a).
In Module 4, Topic C, students manipulate rectangular arrays to concretely demonstrate the arithmetic properties in anticipation of the following lessons. They do this by cutting rectangular grids and rearranging the parts into new wholes using the properties to validate that area stays the same, despite the new dimensions. They apply tiling and multiplication skills to determine all whole number possibilities for the side lengths of rectangles given their areas (3.MD.7b).
Module 4, Topic D creates an opportunity for students to solve problems involving area (3.MD.7b). Students decompose and/or compose composite regions into non-overlapping rectangles, find the area of each region, and add or subtract to determine the total area of the original shape. This leads students to design a simple floor plan that conforms to given area specifications (3.MD.7d).
The area of a rectangle can be found by using unit squares and by multiplying side-lengths. This activity with videos and practice problems will show third-grade students how to think of area in terms of covering an object with square tiles and by multilpying the dimensions.
