11 maths angles in triangles practice
21 October 2026
Angles in triangles
Understanding angles in triangles is an essential skill for 11+ maths. Questions often ask children to find a missing angle using a simple rule. Practising these helps build confidence and accuracy.
The 180° rule
The key fact is that the three angles inside any triangle always add up to 180°. This rule is the foundation for solving all triangle angle questions in the 11+.
Worked example
Imagine a triangle with two known angles: 50° and 60°.
Step 1: Note the given angles. They are 50° and 60°.
Step 2: Remember that all three angles must add up to 180°.
Step 3: Add the known angles: 50 + 60 = 110.
Step 4: Subtract this total from 180° to find the missing angle: 180 - 110 = 70.
The correct answer is 70°.
Key insight: Practising with different triangle diagrams and always using the 180° rule helps children spot patterns and avoid mistakes. Drawing the triangle and labelling angles clearly can make working out the answer much easier.
Keep practising together
Encourage your child to try a range of triangle angle questions. Repetition helps the 180° rule become second nature, making them more confident on test day.
