By the end of the lesson students will define and use a square unit to measure the area of a rectangleCommunicate how they measured the area of a rectangle. Students in first grade practice covering an area with multiple copies of whole units to describe its size. Allow students to work in pairs to estimate, measure, and record the number of each unit it would take to cover the top of one desk. Ask:How can we describe the number of index cards and sheets of notebook paper it would take to cover or tile the desk top? Students are challenged to use just one square unit to measure a surface.