Triangle angle sumThe third angle
Name: Date:
Find the angle marked x. Give each answer in degrees.
1 degrees
2 degrees
3 degrees
4 degrees
5 degrees
6 degrees
Angles in a triangle worksheets
Every triangle's three angles come to 180°, and that one fact answers every question on these sheets. Two angles are printed inside the figure and the third is marked x.
If they get stuck
Angles in a triangle
The answer key prints on a separate page.
What's on this sheet
The arithmetic is one addition and one subtraction, and that is deliberate. What is being learned is the fact itself, and a child who has to fight the numbers to reach it learns the fight instead. Every angle steps in fives, which keeps the mental arithmetic where the standard wants it.
Why this sheet works
The triangles are drawn to their real angles, which means a protractor would answer them — and that is exactly why the third angle is never printed. A figure here may be honest, but it may not be a lookup. The same rule runs through every angle sheet on this site.
How this one works
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Angles in a triangle, step by step