This Instructional Activity is a part of the Lesson 6, Unit 3, Grade 7. In this activity students calculate the area of an irregular shape presented in a scale drawing. In this case, students can calculate the area exactly by composing and decomposing triangles and parallelograms. This activity draws upon MP7 in a geometric context much like the warm-up did in an arithmetic context. Choosing an appropriate way to compose and decompose the floor plan of the house in order to make calculations efficient is analogous to choosing how to rewrite numbers in order to make finding their sum, difference, or product as efficient as possible.