New
New
Year 6

When a 2D shape is decomposed and the parts rearranged, the areas remains the same

I can decompose a 2D shape and create a different shape from the parts and explain why the area of the new compound shape is the same as the original 2D shape.

New
New
Year 6

When a 2D shape is decomposed and the parts rearranged, the areas remains the same

I can decompose a 2D shape and create a different shape from the parts and explain why the area of the new compound shape is the same as the original 2D shape.

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Lesson details

Key learning points

  1. The area of the compound shape is equal to the total areas of its parts
  2. 2D shapes can be decomposed and rearranged in different ways
  3. 2D shapes can be decomposed and rearranged in different ways but the total area stays the same

Keywords

  • Compound shape - A compound shape is a shape created using two or more basic shapes.

  • Area - Area is the measurement of a flat surface. It measures a 2D space.

Common misconception

Children may assume some shapes have a larger area than others by comparison of a certain dimension. In this lesson, pattern blocks can be arranged to create shapes with very different dimensions.

Encourage pupils to rearrange the composing shapes to prove that the compound shapes have the same area. This can be done effectively with tangrams or pattern blocks, both of which feature heavily in this lesson.

It is important pupils have opportunities to manipulate shapes in this lesson and tangrams and pattern blocks are used to this effect. If physical versions are unavailable these manipulatives can be found online for a virtual experience.
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).

Lesson video

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6 Questions

Q1.
Which words describe the smaller shapes the larger square is composed of?
An image in a quiz
Correct answer: Polygons
Correct answer: 2D shapes
Pentagons
3D shapes
Q2.
Which words describe the smaller shapes the larger square is composed of?
An image in a quiz
Correct answer: Square
Pentagon
Correct answer: Parallelogram
Correct answer: Right-angled triangle
Trapezium
Q3.
What is area?
The distance around the edge of a shape.
Correct answer: The measurement of space in a 2D shape.
The number of sides in a shape.
Q4.
Which of these properties must a shape have for it to have an area?
Correct answer: The sides must be closed.
The sides must all be straight.
It must be a square shape.
Q5.
If you decompose a shape, what do you do?
Correct answer: Break it into parts that are the same as the original when put back together.
Put it together from parts.
Reduce its size.
Q6.
Is it possible for two 2D shapes to have the same area?
Correct answer: Yes, as long as they take up the same amount of space.
Yes, as long as they are different types of the same shape,for example triangle.
No, two 2D shapes cannot have the same area.

6 Questions

Q1.
Which of these compound shapes have the same area as each other?
An image in a quiz
Correct Answer: An image in a quiz
An image in a quiz
Correct Answer: An image in a quiz
An image in a quiz
Q2.
The three shapes are composed of parts that are the same size. Select the shapes that have the same area.
Correct answer: Shape A
Shape B
Correct answer: Shape C
Q3.
Select the shapes that have the same area.
Correct Answer: An image in a quiz
An image in a quiz
Correct Answer: An image in a quiz
An image in a quiz
An image in a quiz
Q4.
What can be done so that the shapes have the same area?
An image in a quiz
Remove the parallelogram from shape a.
Correct answer: Add a parallelogram to shape b.
Nothing. They already have the same area.
Q5.
These compound shapes are composed of identical smaller shapes. Which have the same area?
Correct answer: Shape A
Correct answer: Shape B
Shape C
Shape D
Q6.
The two compound shapes have been composed of identical smaller shapes. Which of these statements is true?
An image in a quiz
Correct answer: The shapes have the same area.
The area of a is greater than the area of b.
The area of b is greater than the area of a.
Correct answer: They are both compound shapes.

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