9.05 Order and compare areas

We can work out the  area of a shape  by seeing how many squares fit inside it. Try this question.

Examples

Example 1

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

Each grid square represents 1 square unit.

Worked Solution

Create a strategy

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

Apply the idea

There are 32 shaded squares.

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

Watch question walkthrough

When we  compared length  , we looked at which object was shorter, or longer than the other. We used number lines or lines to help us do this. We can do a similar thing with area, but instead of lines, we use squares.

When we compare area, we can use a square unit to do this. So if we are working with centimetres, we use a square measuring 1\text{ cm} \times 1\text{ cm}. We can use the same method if we working with metres, but instead using a 1\text{ m} \times 1\text{ m} square.

In this video, we'll compare some shapes using a 1\,cm unit square.

Examples

Example 2

Look at the two shapes on the grid.

a

What are the areas of Shape A and Shape B?

Worked Solution

Create a strategy

Count the number of squares shaded for each shape.

Apply the idea

There are 9 squares in shape A.\text{Area of Shape A}=9\text{ square units}

There are 25 squares in shape B.\text{Area of Shape B}=25\text{ square units}

Watch question walkthrough

b

Which is the smallest shape?

Worked Solution

Create a strategy

We can compare the values of areas.

Apply the idea

Since 9 is less than 25, Shape A is the smallest shapes.

Watch question walkthrough

In this video we look at the area of objects in our everyday life, and how we might compare them. Which unit square should we use? What if we were to use a sheet of paper? Let's find out what happens when we do.

Examples

If both our values (numbers) and units of measurement are different, we can use what we know about a unit square to help work out which shape might have the largest area.

Examples