This Problem Set is a part of the Lesson 21, Unit 7, Grade 3. In this lesson, students continue finding the possible areas of rectangles with a given perimeter. They use the same strategy as in the previous lesson, dividing the perimeter by 2 to find the sum of the length and width, which leads to possible dimensions and possible areas. Then they discuss the relationship between area and perimeter of a rectangle, reinforcing many of the understandings from the previous two lessons.