Area, perimeter, and how they're related

Students will learn how to find the perimeter of composite rectangles (rectilinear figures) by adding. They'll also learn how to solve missing number addition problems involving perimeter. Next, students will be given unit squares, as wooden blocks, or otherwise, which they'll use throughout the remainder of this lesson. Students will first use the blocks to find rectangles that have the same perimeter, but different area, and vice-versa. Next, students will use the blocks to learn how to find the dimensions of the rectangle with the smallest/largest perimeter, given its area. By doing several such problems, students should see that perimeter increases as the rectangle flattens. That's because as the rectangle flattens, the number of unit squares whose edges are on the boundary of the rectangle increases. After that, students will use the blocks to find the dimensions of a rectangle given both its area and perimeter, as seen here.