Interior angles of a polygon | Maths | Quizalize & Oak National Academy

Starter quiz

An ______ angle is an angle formed inside a polygon by two of its edges.
- acute
- alternate
- exterior
- interior ✓
- obtuse
The interior angles of a triangle sum to ______°.
- '180' ✓
What is the size of ∠ABC?
- 73°
- 84° ✓
- 95°
- 108°
What is the value of $x$ ? $x=$ ______.
- '49' ✓
Starting with the smallest, sort the angles in ascending order of size.
- 1
  
  ⇔
  
  acute
- 2
  
  ⇔
  
  right angle
- 3
  
  ⇔
  
  obtuse
- 4
  
  ⇔
  
  reflex
What is the size of the angle $x$ °?
- 52° ✓
- 58°
- 64°

A pentadecagon has 15 sides. The minimum number of triangles that it could be split into is ______.
- '13' ✓
An octadecagon has 18 sides. Which calculation would find the sum of its interior angles?
- $16 \times 180$ ✓
- $18 \times 180$
- $20 \times 180$
The interior angles in the hexagon sum to ______°.
- '720' ✓
The interior angles of a pentagon sum to ______°.
- '540' ✓
The size of the angle $x$ ° is ______°.
- '141' ✓
The size of the angle $x$ ° is ______°.
- '112' ✓

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Any polygon can be split into triangles.
Using these triangles you can demonstrate the rule for the interior angle sum of a polygon.
A missing interior angle in any polygon can be found.

When splitting a polygon into triangles, pupils may draw line segments that cross inside the shape.

By choosing a single common vertex for all the triangles, the line segments will not cross inside the shape.

Polygon - A polygon is a flat (2D), closed figure made up of straight line segments.
Interior angle - An interior angle is an angle formed inside a polygon by two of its edges.
Sum - The sum is the total when numbers are added together.