Angles in Quadrilaterals for 11+ Maths
21 October 2026
Understanding quadrilaterals
Quadrilaterals are four-sided shapes such as squares, rectangles, parallelograms and trapeziums.
Every quadrilateral has four interior angles.
Angle facts to remember
The sum of all interior angles in any quadrilateral is always 360 degrees.
In parallelograms, opposite angles are equal. Adjacent angles in a parallelogram add up to 180 degrees.
Worked example
Suppose a quadrilateral has three known angles: 85°, 95°, and 100°.
Step 1: Add the three known angles. 85 + 95 = 180. 180 + 100 = 280.
Step 2: Subtract this sum from 360 to find the missing angle. 360 - 280 = 80.
The correct answer is 80°.
Why practice matters
Key insight: Practising these calculations helps children spot angle relationships and solve for missing angles with confidence, a skill often tested in 11+ exams.
