Find the missing angle in a triangle: worked example
22 October 2026
To solve problems with missing angles in triangles, children need to remember one key fact: the angles in any triangle always add up to 180 degrees. This makes it possible to find a missing angle if you know the other two.
Worked example
A triangle has angles of 65° and 45°. What is the missing angle?
Step 1: Add the two known angles.
65 + 45 = 110
Step 2: Subtract this total from 180 to find the missing angle.
180 - 110 = 70
The correct answer is 70°.
After seeing this example, your child will recognise how to use the 180-degree rule to work out any missing angle in a triangle. They are now ready to try similar questions and build confidence with angles in triangles.
