Angles in triangles · Year 6
In Year 6 you learn: angles in a triangle add to 180°.
The three angles inside any triangle always add up to 180°. Combined with facts about isosceles and equilateral triangles, this lets you find any missing angle, and the exterior-angle rule gives a useful shortcut.
Key facts
- Angles in a triangle add up to 180°.
- In a right-angled triangle the other two angles add up to 90°.
Worked examples
Example 1
Why do the angles in any triangle add up to 180°?
Answer: They fit together on a straight line, and angles on a straight line add up to 180°.
Example 2
Find the angle x.
Answer: x = 60°