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10.07 Find areas

Lesson

Are you ready?

We've used squares and rectangles to help us  compare areas  . Let's try this problem to review.

Examples

Example 1

Which shape has the smallest area?

A
The image shows a formless shape. Ask your teacher for more information.
B
The image shows a formless shape. Ask your teacher for more information.
Worked Solution
Create a strategy

Choose the shape that takes up less space.

Apply the idea

The shape in option A is taking up less space than the shape in option B.

The shape that has the smallest area is option A.

Idea summary

Area is the amount of space taken up by a shape or object.

Compare the areas of shapes

We can measure area in shapes such as squares and rectangles, but what about different shapes?

To help us measure the area of shapes like the ones pictured below, we can use square units.

The image shows 3 different shapes on a grid. Ask your teacher for more information.

In this video, we look at how to calculate the area of shapes similar to those in the picture shown.

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Examples

Example 2

Find the area of the shape by counting the number of grid squares it covers.

A grid with 32 shaded squares that made a larger shape. Ask your teacher for more information.

Each grid square represents 1 square unit.

Worked Solution
Create a strategy

Count the total number of the shaded squares to find the area.

A grid with 32 shaded squares that made a larger shape. Ask your teacher for more information.
Apply the idea

There are 32 shaded squares.

\text{Area}=32 \text{ square units}

Idea summary

We can find the area of a shape on a grid by counting the number of square units.

Compare the areas of other shapes

Sometimes we have unusual shapes but we can still work out the area of these shapes by counting the number of square units inside. We can also work out the area of triangles.

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Examples

Example 3

Find the area of the shape by counting the number of grid squares it covers.

A grid with shaded section in shape of a triangle. Ask your teacher for more information.

Each grid square represents 1 square unit.

Worked Solution
Create a strategy

Count the total number of fully shaded squares and combine the half shaded squares to make 1 square unit.

A grid with shaded section in shape of a triangle. Ask your teacher for more information.
Apply the idea

There are 2 shaded squares and 4 halves. The 4 halves can be combined to make 2 more shaded squares:

A grid with 4 shaded squares forming a square. Ask your teacher for more information.
\displaystyle \text{Area}\displaystyle =\displaystyle 2 + 2Add all the squares
\displaystyle =\displaystyle 4 \text{ square units}
Idea summary

To find the amount of space a shape takes up, we can use a grid to count the number of unit squares that it covers.

Find the area of shapes with unit squares

This video shows us how to use unit squares to find the area.

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Examples

Example 4

Find the area of the shape below.

The image shows an L shape made up of 5 squares. Ask your teacher for more information.
Worked Solution
Create a strategy

Count the total number of squares.

Apply the idea

There are 5 squares inside the shape.

\text{ Area }= 5 \text{ units}^2

Idea summary

To find the amount of space a shape takes up, we can use a unit square.

Outcomes

MA3-10MG

selects and uses the appropriate unit to calculate areas, including areas of squares, rectangles and triangles

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