NumihanaA triangle has angles 80° and 40°. Find its third angle.
Answer: ________________
LEARN, PRINT & PRACTISE
Missing angles in triangles.
Missing angles in triangles
Numihana · England Year 6
Missing angles in triangles
Practice sheet
Name: ______________
Date: ______________
Missing angles in triangles
A triangle has angles 60° and 50°. Find its third angle.
Answer: ________________
A triangle has angles 50° and 60°. Find its third angle.
Answer: ________________
A triangle has angles 60° and 40°. Find its third angle.
Answer: ________________
A triangle has angles 40° and 70°. Find its third angle.
Answer: ________________
A triangle has angles 30° and 60°. Find its third angle.
Answer: ________________
Numihana · England Year 6
Missing angles in triangles
Answer key
Name: ______________
Date: ______________
Missing angles in triangles
A triangle has angles 80° and 40°. Find its third angle.
Answer: 60
A triangle has angles 60° and 50°. Find its third angle.
Answer: 70
A triangle has angles 50° and 60°. Find its third angle.
Answer: 70
A triangle has angles 60° and 40°. Find its third angle.
Answer: 80
A triangle has angles 40° and 70°. Find its third angle.
Answer: 70
A triangle has angles 30° and 60°. Find its third angle.
Answer: 90
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The skill behind this activity
Missing angles in triangles
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 triangle has angles 70° and 50°. Find its third angle.
Answer: 60
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.