 # 2.01 Single digit fact families

Lesson

## Ideas

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.

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.

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.

### Examples

#### Example 2

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

a

What is 2 + 5?

Worked Solution
Create a strategy

Use the fact family below:

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:

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:

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.

### Outcomes

#### MA2-5NA

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers