Topics
2. Forwards and backwards
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Australia
Year 3

2.01 Single digit fact families

Lesson
Practice
Lesson

Are you ready?

Do you remember how to add numbers together, like 3 and 4?

Examples

Example 1

The image below shows one group of apples being added to another.

Image of three apples and four apples with a plus sign in between the two groups of apples.

How many apples are there in total?

Worked Solution
Create a strategy

Start with the number in the first group and count up the number from the second group.

Apply the idea

There are 3 apples in the first group and 4 apples in the second group.

Start at 3 and count up by 4 to get: 3 + 4 = 7

There are 7 apples in total.

Reflect and check

We can also find the sum of 3 + 4 using the number line below by starting from 3 and then counting up 4 places to get to 7.

012345678910
Idea summary

To add numbers together, we can use counting or the number line.

Fact families for addition and subtraction

Let's see how 3, 4 and 7 are related and make a fact family.

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Examples

Example 2

Here is the fact family of 2, 5 and 7.

Image of five squares plus two squares equals seven squares. Ask your teacher for more information.
a

What is 2 + 5?

Worked Solution
Create a strategy

Use the fact family below:

Two rows of seven squares. Ask your teacher for more information.
Apply the idea

From the fact family above, we can see that 5 + 2 is the same as 7.

So, 2 + 5 = 7.

b

What is 7 - 5?

Worked Solution
Create a strategy

Use the fact family below:

Two rows of seven squares. Ask your teacher for more information.
Apply the idea

We know that 5 + 2 = 7.

If we take away 5 from 7, there will be 2 left.

So we have:

7 - 5 = 2

c

What is 7 - 2?

Worked Solution
Create a strategy

Use the fact family below:

Two rows of seven squares. On the second row five squares has a different colors with the two squares.
Apply the idea

We know that 5 + 2 = 7.

If we take away 2 from 7, there will be 5 left.

So we have:

7 - 2 = 5

Idea summary

A fact family has three numbers that are connected in some way. In this case, they are connected by addition and subtraction.

Addition and subtracton of 6 and 3. Ask your teacher for more information.

Outcomes

AC9M3A01

recognise and explain the connection between addition and subtraction as inverse operations, apply to partition numbers and find unknown values in number sentences

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