Reasoning about angles in polygons

I can reason about the sum of the angles within different polygons.

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Year 5

Reasoning about angles in polygons

I can reason about the sum of the angles within different polygons.

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Share activities with pupils

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Slide deck

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Lesson details

Key learning points

Angles describe and measure a turn or rotation.
Protractors can be used to measure and draw angles.
Use knowledge of right angles to estimate and compare angles.

Keywords

Angle - An angle is a measure of turn.
Sum - The sum is the result of adding two or more numbers.
Vertex - A vertex is a point where two or more lines meet.
Polygon - A polygon is a 2D shape made up of three or more straight lines.

Common misconception

Pupils think that composing larger polygons of smaller triangles that are not formed as a result of drawing a line from one vertex to another will help them to identify the sum of the angles.

Highlight how the formation of triangles within a polygon must be from vertex to vertex and demonstrate how the angles of each triangle where they meet sum to the internal angle of the polygon.

Avoid expecting pupils to have learnt the sum of the internal angles in a range of different shapes as known facts. This is not an expectation for the curriculum, so provide pupils with information on this or encourage them to calculate these. The diagrams in this slide deck are not drawn to scale.

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Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).