Addition and Subtraction

NZ Level 2

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.

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

$+$+ | $=$= | |||

$8$8 | $+$+ | $1$1 | $=$= | $9$9 |

What is $1+8$1+8?

What is $9-8$9−8?

What is $9-1$9−1?

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

$-$− | $=$= | |||

$6$6 | $-$− | $4$4 | $=$= | $2$2 |

What is $2+4$2+4?

What is $6-2$6−2?

What is $4+2$4+2?

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

$+$+ | $=$= | ? | ||

$2$2 | $+$+ | $4$4 | $=$= | ? |

What is $2+4$2+4?

What is $4+2$4+2?

What is $6-4$6−4?

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

Yes

ANo

BYes

ANo

BWhat is $6-2$6−2?

Know the basic addition and subtraction facts