Triangles can still be different sizes
The size can change without changing the name of the shape.
3 sides3 vertices
same propertiesdifferent size
Use the properties first.
Year 4
Compare and classify geometric shapes, including quadrilaterals and triangles, based on their properties and sizes
Use sides, angles, parallel lines and symmetry to sort triangles and quadrilaterals.
Lesson overview
Geometry - properties of shape
Shapes can be classified by their properties. Useful properties include the number of sides, equal sides, right angles, parallel sides and lines of symmetry.
Squares and rectangles are quadrilaterals
Quadrilateral means a shape with 4 sides.
4 equal sides4 right angles
4 sides4 right angles
Both shapes belong in the quadrilateral group.
One shape can fit more than one group
A square is a quadrilateral and also has 2 pairs of parallel sides.
quadrilateral
square fits
square and rectangle fit
Check all the properties.
Worked example
Why is a square also a quadrilateral?
- Quadrilateral means a shape with 4 sides.
- A square has 4 sides.
- So a square belongs in the quadrilateral group.
- It also has extra properties such as equal sides and right angles.
Round 1: Learn it
Use the shape properties to decide which group each shape belongs to.
Finish this round to unlock Round 2: Show you know it.
Question 1
Which shape is a quadrilateral?
4 sides
Question 2
Which statement about a square is correct?
equal sidesright angles
Question 3
How many sides does a quadrilateral have?
count the sides
Question 4
Which pair are both quadrilaterals?
4 sides
4 sides
3 sides
Question 5
Which reminder is correct?
Common mistakes
Watch for these as you work through the lesson.
- Thinking a larger square stops being a square.
- Forgetting that all quadrilaterals have 4 sides.
- Sorting by only one property when more than one matters.
Related topics
These ideas connect closely to this lesson.
- Identify lines of symmetry in 2-D shapes presented in different orientations.
- Complete a simple symmetric figure with respect to a specific line of symmetry.