Lesson Plan

Explain that when an angle is decomposed into non-overlapping parts, the angle measure of the whole equals the sum of the angle measures of the parts

Decompose a given angle into two or more non-overlapping smaller angles and write an addition equation relating the part measures to the whole measure

Write and solve addition and subtraction equations with a symbol for an unknown angle measure, using a diagram as the source of information

Apply the additive property of angle measure to find unknown angles in real-world and mathematical contexts, including angles on a straight line (180 degrees) and angles around a point (360 degrees)

Verify solutions by checking that the computed part measures sum to the known whole measure

4.MD.C.7

4.MD.C.7: Recognize angle measure as additive. When an angle is decomposed into non-overlapping parts, the angle measure of the whole is the sum of the angle measures of the parts. Solve addition and subtraction problems to find unknown angles on a diagram in real world and mathematical problems, e.g., by using an equation with a symbol for the unknown angle measure.