This Problem Set is a part of the Lesson 5, Unit 4, Grade 3. In this lesson, students find the area of a rectangle with whole-number side lengths by tiling it, and show that the area is the same as would be found by multiplying the side lengths. Then they create two adjacent sides of a rectangle and predict the area of the entire rectangle by multiplying the side lengths. Finally, they find a side length of a rectangle given its area and the length of an adjacent side.