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.
Students will learn what it means for two angles to be adjacent, and after that, what the additive property of angles is. Then students will be asked to identify adjacent angles in geometric figures, and to use the additive property of angles, to find the measure of some angle, in a geometric figure or word problem.