# Connect addition and subtraction

Lesson

When we add two numbers together, we create an addition fact, such as $8+7=15$8+7=15.  We can also make other facts with these three numbers, and use them to explore how addition and subtraction are related. In the video we explore fact families and related facts, all using just three numbers.

#### Worked Examples

##### Question 1

Consider these three numbers:

 $4$4 $8$8 $4$4
1. Write a number sentence of the form

 $\editable{}+\editable{}=\editable{}$+=

that uses ADDITION to connect the three numbers.

2. Now write a number sentence of the form

 $\editable{}-\editable{}=\editable{}$−=

that uses SUBTRACTION to connect the three numbers.

##### question 2

Answer the following questions.

1. Consider these numbers:

 $4$4 $5$5 $9$9

Write a number sentence that uses ADDITION to connect the three numbers.

2. Now consider these numbers:

 $8$8 $1$1 $7$7

Fill in the boxes below to write TWO number sentences that use ADDITION to connect the three numbers.

$\editable{}+1=\editable{}$+1=

$\editable{}+7=\editable{}$+7=

3. Consider the same numbers as you saw in the last question:

 $8$8 $1$1 $7$7

Write TWO number sentences of the form

 $\editable{}-\editable{}=\editable{}$−=

that use SUBTRACTION to connect the three numbers.

##### question 3

Answer the following questions:

1. Consider these numbers:

 $4$4 $10$10 $6$6

Write a number sentence that uses ADDITION to connect the three numbers.

2. Now consider these numbers:

 $20$20 $2$2 $18$18

Fill in the boxes below to write TWO number sentences that use ADDITION to connect the three numbers.

$\editable{}+18=\editable{}$+18=

$\editable{}+2=\editable{}$+2=

3. Consider the same numbers as you saw in the previous part:

 $20$20 $2$2 $18$18

Write TWO number sentences of the form

 $\editable{}-\editable{}=\editable{}$−=

that use SUBTRACTION to connect the three numbers.

Enter both number sentences on the same line, separated by a comma.