New
New
Year 5

Reasoning about angles in polygons

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

New
New
Year 5

Reasoning about angles in polygons

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

Lesson details

Key learning points

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

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.

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.

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).

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6 Questions

Q1.
Look at the hands on this clock face and the arrow. The angle formed is __________.
An image in a quiz
acute
obtuse
obtuse
Correct answer: reflex
Q2.
Where two lines create an angle within a shape, we call this part a .
An image in a quiz
Correct Answer: vertex
Q3.
The angles in a triangle sum to ___.
An image in a quiz
90°
Correct answer: 180°
270°
360°
Q4.
The angles in a quadrilateral sum to ___.
An image in a quiz
90°
180°
270°
Correct answer: 360°
Q5.
Fill in the missing product 3 × 180 =
Correct Answer: 540
Q6.
The triangle is not to scale. The missing angle labelled m is °
An image in a quiz
Correct Answer: 110

6 Questions

Q1.
What do these lines represent on two sides of this polygon?
An image in a quiz
Correct answer: The length of both lines are the same.
The markers divide each line into two parts.
The length of both lines are different.
Q2.
Any polygon can be always be divided into what other type of polygon?
Circles
Rectangles
Correct answer: Triangles
Squares
Q3.
You can work out the sum of the angles in a polygon by:
Multiplying the number of angles by 180
Correct answer: Multiplying the number of internal triangles by 180
Dividing 180 by the number of angles.
Q4.
The size of missing angle a is degrees.
An image in a quiz
Correct Answer: 108
Q5.
A triangle is placed inside a rectangle. Tick the calculation that helps to find missing angle b.
An image in a quiz
180° − 46°
Correct answer: (180° − 46°) ÷ 2
180° ÷ 2 − 46°
Q6.
A triangle is placed inside a rectangle. The size of missing angle c is degrees.
An image in a quiz
Correct Answer: 23