Lesson plan

Decompose angles by examining a real-world situation

teaches Common Core State Standards CCSS.Math.Content.4.MD.C.7 http://corestandards.org/Math/Content/4/MD/C/7
teaches Common Core State Standards CCSS.Math.Practice.MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards CCSS.Math.Practice.MP7 http://corestandards.org/Math/Practice/MP7

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Big Ideas: Angles can be decomposed into smaller parts. Angle measure of the whole is the sum of the angle measures of the parts. This lesson builds on students' knowledge of measuring angles. The task asks students to take a 40-degree skateboard ramp and decompose it into smaller parts. Through exploration of a variety of smaller angles (5°, 10°, 15°, and 20°), students will see that there are many combinations of smaller angle measures that total 40 degrees, leading students to an understanding of decomposing and composing angles. They will see that a protractor is not needed to decompose an angle. Their work in decomposing angles builds towards students' future work in discovering that angles are additive. Vocabulary: angle, compose, decompose, degree