# Addition fact families (a+b=c, c-b=a)

Lesson

A fact family describes a relationship between 3 numbers.  The relationship could be through addition or subtraction.

This video shows how we can use fact families to help us answer questions.

#### Worked Examples

##### Question 1

We are interested in the fact family of $1$1,$8$8 and $9$9.

 $+$+ $=$= $8$8 $+$+ $1$1 $=$= $9$9
1. What is $1+8$1+8?

2. What is $9-8$98?

3. What is $9-1$91?

##### Question 2

We are interested in the fact family of $2$2, $4$4 and $6$6:

 $-$− $=$= $6$6 $-$− $4$4 $=$= $2$2
1. What is $2+4$2+4?

2. What is $6-2$62?

3. What is $4+2$4+2?

##### Question 3

We are interested in the fact family of $2$2,$4$4 and $6$6:

 $+$+ $=$= ? $2$2 $+$+ $4$4 $=$= ?
1. What is $2+4$2+4?

2. What is $4+2$4+2?

3. What is $6-4$64?

4. When looking at the answer to $6-2$62, is the answer going to be less than $10$10?

Yes

A

No

B

Yes

A

No

B
5. What is $6-2$62?

### Outcomes

#### NA2-3

Know the basic addition and subtraction facts