New
New
Year 6

Reason about compound shapes using the relationship between side lengths and area and perimeter

I can reason about compound shapes using the relationship between side lengths and area and perimeter.

New
New
Year 6

Reason about compound shapes using the relationship between side lengths and area and perimeter

I can reason about compound shapes using the relationship between side lengths and area and perimeter.

Lesson details

Key learning points

  1. Area and perimeter are calculated from the side lengths of 2D shapes.
  2. Area and perimeter are measured in different units.
  3. Compound shapes can be decomposed and rearranged in different ways.

Common misconception

The numbers used as side lengths in this lesson are generally relatively low, and based around times tables. As a result, pupils might be tempted to guess / estimate the missing side lengths.

Remind pupils that the shapes are not to scale and encourage them to use subtraction skills instead - what is the difference between this known side length and this known side length?

Keywords

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

  • Dimension - A dimension is a measurement of length in one direction.

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).

Loading...

6 Questions

Q1.
Select all of the statements that are true of this number shape.
An image in a quiz
Correct answer: It has a perimeter.
Correct answer: It is a compound shape.
Its outline forms a regular shape.
Correct answer: It can be decomposed into two rectangles.
Q2.
Laura says the perimeter of this shape is 8 units. What mistakes do you think she has made?
An image in a quiz
Counted one side twice.
Correct answer: Not counted all of the sides.
Correct answer: Counted the squares inside the shape, giving the area.
Q3.
What is the perimeter of this rectangle? cm
An image in a quiz
Correct Answer: 72
Q4.
What is the perimeter of this shape? Remember to include the correct units.
An image in a quiz
Correct Answer: 206 cm
Q5.
What is the missing side length of this rectangle? Remember to include the correct units.
An image in a quiz
Correct Answer: 5 cm
Q6.
What is the area of this square? cm$$ ^2 $$
An image in a quiz
Correct Answer: 144

6 Questions

Q1.
Give the missing side length. cm
An image in a quiz
Correct Answer: 2
Q2.
Give the missing side length. cm
An image in a quiz
Correct Answer: 5
Q3.
Is there enough information to calculate the perimeter of the shape?
An image in a quiz
Yes. Add the known side lengths together.
Correct answer: No. Two of the side lengths are missing.
No. One of the side lengths is missing.
Q4.
Calculate the perimeter of the shape. cm
An image in a quiz
Correct Answer: 26
Q5.
The area of the shape is 43 cm². Order the steps to work out the missing dimension.
An image in a quiz
1 - Calculate the area of one rectangle by multiplying its known side lengths.
2 - Subtract the area of the known rectangle from the known area.
3 - Divide the area of the other rectangle by its known side length.
Q6.
The area of the shape is 43 cm². What is the missing side length?
An image in a quiz
Correct Answer: 2 cm