This Problem Set is a part of the Lesson 22, Unit 7, Grade 3. In this lesson, students create a line plot showing the number of rectangles with a given perimeter they created during the previous two lessons. Then they make observations about the data in order to better understand the relationships between side lengths and perimeter. (For example, they notice that all of their rectangles have even perimeters, and determine that this is because they have whole-number side lengths.)