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Year 3

Identify properties of triangles

I can use different properties to identify and sort triangles.

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New
New
Year 3

Identify properties of triangles

I can use different properties to identify and sort triangles.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Triangles always have three sides, vertices and angles.
  2. Triangles always have straight sides and sharp vertices.
  3. Triangles can have right angles.
  4. Vertices are the corners of a shape.

Common misconception

Pupils may see other shapes and collections of lines as triangles when they are not (e.g. shapes with rounded corners, three lines that do not all meet).

Provide pupils with shapes, and explore shapes in the environment, classifying them as 'triangles' and 'not triangles'. Ask children, 'Does this shape have three straight sides? Does it have clearly defined, sharp vertices?'

Keywords

  • Triangle - A polygon with three straight sides.

  • Vertex - The point where two lines meet.

  • Vertices - More than one vertex.

  • Properties - A character or quality that something has.

Pupils will already have some familiarity with triangles but this lesson helps them to define what a triangle is. Pupils begin to classify and sort triangles by their angles, length of sides and whether they have reflective symmetry or not. The sorting provides opportunities for pupil discussion.
Teacher tip

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).

Video

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Starter quiz

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6 Questions

Q1.
Which of these images shows a right angle?
An image in a quiz
Correct answer: a
b
c
Correct answer: d
Q2.
A right angle is the same as a turn.
Correct answer: quarter
half
three-quarter
whole
Q3.
How many right angles does this shape have?
An image in a quiz
Correct answer: 0
1
2
3
Q4.
Look at this triangle. Which of these statements are true?
An image in a quiz
Correct answer: The shape does have reflective symmetry.
Correct answer: The shape has 1 line of symmetry.
The shape has 2 lines of symmetry.
The shape has 3 lines of symmetry.
Q5.
Which letter does not have at least one right angle?
An image in a quiz
E
H
T
Correct answer: Z
Q6.
Which shapes have at least one right angle?
An image in a quiz
a
Correct answer: b
c
d

Exit quiz

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6 Questions

Q1.
The corners of a shape are called the .
properties
symmetry
Correct answer: vertices
right angles
Q2.
Which of these shapes are triangles?
An image in a quiz
Correct answer: a
b
c
Correct answer: d
Q3.
Which of these statements are true for all triangles?
Correct answer: They have 3 straight sides.
They have 3 rounded vertices.
They have two sides the same length.
Q4.
Which triangle is exactly the same size and shape as shape a)?
An image in a quiz
b
c
Correct answer: d
e
Q5.
Which triangles have one right angle?
An image in a quiz
Correct answer: a
Correct answer: b
c
d
Q6.
Which triangles have at least two sides the same length?
An image in a quiz
a
Correct answer: b
c
Correct answer: d