Angles in triangles | Maths | Quizalize & Oak National Academy

Starter quiz

Look at the hands on this clock face and the arrow. The angle formed is __________.
- acute ✓
- a right angle
- obtuse
- reflex
This triangle has three equal sides and three equal vertices. Select the correct name for this triangle.
- Equilateral triangle ✓
- Isosceles triangle
- Scalene triangle
Match the angles to the correct description
- Smallest angle
  
  ⇔
  
  A ✓
- Second largest angle
  
  ⇔
  
  B ✓
- Third largest angle
  
  ⇔
  
  C ✓
- Largest angle
  
  ⇔
  
  D ✓
The image is not to scale. What is the value of missing angle a? a = ______°
- '106' ✓
The image is not to scale. What is the value of missing angle a? a = ______°
- '42' ✓
The image is not to scale. What is the value of missing angle a? a = ______°
- '197' ✓

Exit quiz

The internal angles in all triangles sum to ___.
- 90°
- 180° ✓
- 360°
Tick the expressions that could represent the angles in a triangle.
- 90°+ 25° + 65° ✓
- 90°+ 30° + 30°
- 90°+ 40° + 50° ✓
- 90°+ 90°
Tick the expressions that could represent the angles in a triangle.
- 75°+ 45° + 45°
- 70°+ 10° + 100° ✓
- 60°+ 60° + 60° ✓
- 50°+ 48° + 42°
Finish the expression so that it could represent the angle sum of a triangle. 60°+ 75° + ______°
- '45' ✓
The image is not to scale. Calculate missing angle a. A = ______°
- '23' ✓
The image is not to scale. Calculate missing angle a. A = ______°
- '50' ✓

Worksheet

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Presentation

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Lesson Details

Key learning points

Angles on a straight line sum to 180 degrees.
Interior angles in triangles sum to 180 degrees.
Missing angles can be calculated using the sum of 180 degrees.

Common misconception

Pupils struggle to remember the number of degrees in a triangle as they only know it as a disconnected fact.

Apply pupils' knowledge of angles in a quadrilateral to understanding the sum of the angles in a triangle. Spend time showing how a quadrilateral is constructed using triangles and what happens to the angles as the quadrilateral is partitioned.

Keywords

Quadrilateral - A quadrilateral is a polygon with four straight sides and four vertices.
Triangle - A triangle is a polygon with three straight sides and three vertices.
Sum - The sum is the result of adding two or more numbers.