How can you tell they’ve got it: Angle sums in triangles and polygons?

If they’ve got it, you’ll see things like: Calculate a missing angle in a triangle by subtracting the known angles from 180°; Find the sum of interior angles in a hexagon by dividing it into triangles; Calculate each interior and exterior angle of a regular polygon given the number of sides. Or just try it together: If your child knows two angles of a triangle are 50° and 70°, can they work out the third? And can they figure out the angles inside a regular pentagon?

Mathematics Geometry Ages 11–14

Angle sums in triangles and polygons

Your child can find missing angles in triangles and other shapes. Angles in a triangle add to 180°; they can find the angles in a pentagon too.

In curriculum terms

Derive and use the angle sum in a triangle (180°), use it to deduce the angle sum in any polygon ((n−2) × 180°), and calculate interior and exterior angles of regular polygons

Ages are typical, not deadlines — follow your child’s pace. How to help at home →

How to tell they’ve got it

Tick these off as you see them — no test required.

Calculate a missing angle in a triangle by subtracting the known angles from 180°
Find the sum of interior angles in a hexagon by dividing it into triangles
Calculate each interior and exterior angle of a regular polygon given the number of sides

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Try this together

If your child knows two angles of a triangle are 50° and 70°, can they work out the third? And can they figure out the angles inside a regular pentagon?

Where this sits on the map

Stuck here? Check the skills it builds on first. Confident? Here’s what it unlocks.

Builds on

Angles in trianglesages 10–11Extends KS2 angle sums in triangles and quadrilaterals to general polygons

Understanding anglesages 11–13Polygon angle sums require fluency with basic angle properties

Algebraic Notationages 11–12Expressing angle sum as (n-2)×180 requires algebraic notation for the general formula

Angle sums in triangles and polygonsthis skill · ages 11–14

Unlocks

Types of anglesages 13–14Pythagoras requires understanding triangle angle sums and properties

solid = must come firstdashed = helps

Curriculum alignment

Where this fits in the official school curriculum — our best automated guess, not yet checked by a person.

Show candidate curriculum codes · 1 NSW · 2 VIC

Australian Curriculum v9 candidate

This skill sits outside the F–6 Australian Curriculum — no candidate code matched (v0.1).

NSW syllabus codes & stages only

MA3-GM-03low confidenceMathematics K-10 · Stage 3

Victorian Curriculum 2.0 codes & levels only

VC2M5M04low confidenceMathematics · Level 5 · Measurement strand

VC2M6M04low confidenceMathematics · Level 6 · Measurement strand

These are candidate alignments generated by semantic matching — machine-suggested and unreviewed (v0.1), not official or verified mappings. For official curriculum content see australiancurriculum.edu.au, curriculum.nsw.edu.au and f10.vcaa.vic.edu.au. Don’t rely on them for registration or compliance purposes.

Nearby on the map

3-D shapesages 11–13 Angles in trianglesages 11–14 Coordinate Transformationsages 11–14 Measuring anglesages 11–13

All Geometry skills →