Lesson objective: Solve problems with unknown angle measurements using addition and subtraction.
This lesson provides an opportunity for students to apply their knowledge and understanding of angles to a reallife situation. Students are asked to determine unknown angle measurements when given an angle measurement.
Key Concept students will use:
 solve addition and subtraction problems to find unknown angles on a diagram in real world and mathematical problems by using an equation with a symbol for the unknown
Skills students will use:
 recognize angle measure is additive
 understand concepts of angles and measure angles (Grade 4, Unit 10)

an angle is measured with reference to a circle with its center at the common endpoint of the rays, by considering the fraction of the circular arc between the points where the two rays intersect the circle (Grade 4, Unit 10)
Students engage in Mathematical Practice 1 (make sense of problems and persevere in solving them) as they use knowledge of angle types and measurements to solve for unknown angles.
Key vocabulary:
 angle
 compose
 decompose
 right angle
 straight angle