Properties of Triangles: Exercises for 11+ Success
19 October 2026
Understanding triangle properties
Triangles are three-sided shapes found throughout 11+ Maths. Key properties include: the sum of the interior angles is always 180°, the longest side sits opposite the largest angle, and the sum of any two sides is always greater than the third side.
Key insight: Mastering these basics helps children solve many triangle questions confidently.
Angle sum exercises
Ask your child to find the missing angle in a triangle. For example: If two angles are 70° and 50°, what is the third? (Answer: 60°, since 70 + 50 + 60 = 180.) Try with different combinations to build fluency.
Identifying triangle types
Practise classifying triangles by their sides and angles. For example: Draw or spot equilateral (all sides equal), isosceles (two sides equal), and scalene (no sides equal) triangles. Discuss what makes each type unique.
Side length reasoning
Challenge your child with questions about possible triangle sides. For example: Can a triangle have sides 3 cm, 4 cm, and 8 cm? (No, because 3 + 4 is not greater than 8.) This builds understanding of the triangle inequality rule.
Key insight: Applying side rules prevents common mistakes in problem-solving.
Exterior angles practice
Give questions where your child finds an exterior angle, knowing it equals the sum of the two opposite interior angles. For example: If a triangle has angles 50° and 60°, what is the exterior angle at the third vertex? (Answer: 110°, since 50 + 60 = 110.)
