NumihanaA quadrilateral has angles 40°, 80° and 80°. Find its fourth angle.
Answer: ________________
LEARN, PRINT & PRACTISE
Missing angles in quadrilaterals.
Missing angles in quadrilaterals
Numihana · England Year 6
Missing angles in quadrilaterals
Practice sheet
Name: ______________
Date: ______________
Missing angles in quadrilaterals
A quadrilateral has angles 70°, 60° and 20°. Find its fourth angle.
Answer: ________________
A quadrilateral has angles 20°, 50° and 50°. Find its fourth angle.
Answer: ________________
A quadrilateral has angles 70°, 20° and 20°. Find its fourth angle.
Answer: ________________
A quadrilateral has angles 40°, 70° and 40°. Find its fourth angle.
Answer: ________________
A quadrilateral has angles 40°, 20° and 70°. Find its fourth angle.
Answer: ________________
Numihana · England Year 6
Missing angles in quadrilaterals
Answer key
Name: ______________
Date: ______________
Missing angles in quadrilaterals
A quadrilateral has angles 40°, 80° and 80°. Find its fourth angle.
Answer: 160
A quadrilateral has angles 70°, 60° and 20°. Find its fourth angle.
Answer: 210
A quadrilateral has angles 20°, 50° and 50°. Find its fourth angle.
Answer: 240
A quadrilateral has angles 70°, 20° and 20°. Find its fourth angle.
Answer: 250
A quadrilateral has angles 40°, 70° and 40°. Find its fourth angle.
Answer: 210
A quadrilateral has angles 40°, 20° and 70°. Find its fourth angle.
Answer: 230
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The skill behind this activity
Missing angles in quadrilaterals
Department for Education: mathematics programmes of study ↗
Year 6 → Geometry → Properties of shapes · Selected statutory skill. Pack 2.2.0 · source checked 2026-10-12.
For teachers and parents
Use 180 degrees for a triangle and 360 for a quadrilateral. Subtract the other angles from the total. Opposite angles made by crossing straight lines are equal.
A common slip
Choose the correct relationship rather than treating every angle sum as 180.
Worked example
A quadrilateral has angles 50°, 60° and 30°. Find its fourth angle.
Answer: 220
Use 180 degrees for a triangle and 360 for a quadrilateral. Subtract the other angles from the total. Opposite angles made by crossing straight lines are equal.