Finding Missing Angles
Free to teach as-is — the teacher guide, student handout, and slides are included.
Free — we'll email you an access link. Google Docs format.
Objective
I can calculate the measure of an unknown angle that is supplementary to a known angle.
Part 1 of 4
Warm-up video
Kayla Jones · 3:17
We don't generate video — this one is by Kayla Jones on YouTube. The practice questions and exit ticket below were drafted by AI for this objective, and every question is editable in the teacher guide.
Part 2 of 4
Key concepts
3 concepts
- 1
Supplementary angles are two or more angles that add up to 180 degrees.
- 2
If two angles are supplementary, you can set up an equation where the sum of the angles equals 180° and then solve for the unknown angle.
- 3
When parallel lines are cut by a transversal, angles on a flat line are supplementary, meaning their measures add up to 180 degrees, allowing you to solve for variables like x.
Part 3 of 4
Practice
11 questions
What is the measure of an angle that is supplementary to a 60° angle?
If angle A and angle B are supplementary, and the measure of angle A is 115°, what is the measure of angle B?
Part 4 of 4
Exit ticket
Quick comprehension check
“Angle A and angle B are supplementary angles. If the measure of angle A is 123°, what is the measure of angle B?”
Sample answer included in the free materials
Get the materials
Teacher guide, student handout, and slides — free, in Google Docs format
Teacher Guide
Complete lesson plan with answer keys and alternate activities
Student Handout
Printable worksheet
Slides
Ready to present
We'll ask for your email to send your access link — nothing else.
Teaching a group at a different level?
Where are your students right now? We'll rebuild this lesson to match — including the teacher guide, student handout, and slides, saved to your Google Drive.
Adapt This Lesson