Topics
9. Shapes and position
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Australia
Year 4

9.02 Splitting 2D shapes

Lesson
Practice
Lesson

Are you ready?

Let's review the  names of 2D shapes  .

Examples

Example 1

What is the name of the shape below?

The image shows a rectangle.
A
Triangle
B
Rectangle
Worked Solution
Create a strategy

Think of a shape that has 2 pairs of opposite sides with equal lengths.

Apply the idea

From the option above, the shape that has 2 pairs of opposite sides with an equal length is a rectangle.

So the correct option is B: Rectangle

Idea summary

To help work out the name of a shape, think about properties like:

  • How many sides it has

  • What sides are the same length

Split 2D Shapes

Let's look at how some familiar 2D shapes can be broken up into other shapes.

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Examples

Example 2

The shape below can be made up of which three shapes?

The image shows an irregular shape. Ask your teacher for more information.
A
The image shows 2 triangles and a horizontal rectangle. Ask your teacher for more information.
B
The image shows 2 triangles.
C
The image shows 2 triangles and a vertical rectangle. Ask your teacher for more information.
Worked Solution
Create a strategy

Slice the shape to see what shapes we can make.

Apply the idea

We can break up the shape like this:

An irregular shape with a dotted line breaking it into 2 triangles and 1 horizontal rectangle.

After breaking up the dotted line on the shape, we have 2 triangles and 1 horizontal rectangle. So, the correct option is A.

Idea summary

If we start with a two dimensional (2D) shape, we can break it into other 2D shapes.

Combine 2D shapes

Let's go the other way and put shapes together to build other shapes. It's kind of like a puzzle.

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Examples

Example 3

The five shapes below can be combined to make which of the following composite shapes?

The image shows 4 triangles and 1 square.
A
The image shows a shape with 4 points. Ask your teacher for more information.
B
The image shows an irregular shape with 5 points. Ask your teacher for more information.
Worked Solution
Create a strategy

Think about which shape can be made with 4 triangles and 1 square.

Apply the idea

The shape in option A is made up of 4 triangles and 1 square.

The shape in option B is made up of 3 triangles.

So, the correct answer is option A.

Idea summary

We can join, or combine, shapes together to make new shapes.

Outcomes

ACMMG088

Compare and describe two dimensional shapes that result from combining and splitting common shapes, with and without the use of digital technologies

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