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

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$9−8?

3. What is $9-1$9−1?

Reveal SolutionWatch video

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$6−2?

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

Reveal SolutionWatch video

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$6−4?

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

   Yes

   A

   No

   B

5. What is $6-2$6−2?

Reveal SolutionWatch video