 # 4.06 Subtraction 2

Lesson

## Ideas

Do you feel that you have mastered  addition problems  , using some different methods?

### Examples

#### Example 1

Find the value of 720 + 250.

Worked Solution
Create a strategy

Use a number line and plot the bigger number and jump to the right by the smaller number.

Apply the idea

Locate where 720 is.

Note that each space represents 10 units.

Jump 250 units to the right from 720.

We end up at the number 970. So: 720 + 250 = 970

Idea summary

We can use a number line to add numbers, by plotting the larger number then jumping to the right by the smaller number.

## Subtraction with place value models and columns

Just like addition, we can use place value blocks (also called base 10 models) to solve addition. See how we do this in this video.

We can also use place value columns to solve subtraction problems working down our page. In this video we look at subtracting a number in the thousands from another number in the thousands.

### Examples

#### Example 2

Use the number line to find the answer to 667 -637

a

First place 667 on the number line.

Worked Solution
Create a strategy

Notice that each space represents 1 unit.

Apply the idea

667 is 2 more than 665. Place a dot two spaces after 665.

b

Place 637 on the number line.

Worked Solution
Apply the idea

637 is 2 more than 635. Place a dot two spaces after 635.

c

Use the number line to work out the difference between 667 and 637.

Worked Solution
Create a strategy

Count the number of spaces between the two points on the number line.

Apply the idea

667 and 637 have the same units digit. So we can count the difference between them by jumping to the left by tens on the number line from 637 to 667.

3 jumps of ten = 3 \times 10 = 30

667 - 637 = 30

Idea summary

When we are subtracting down the page, it's really important to start from the right (ones place) and work to the left, no matter how many digits our numbers have.

### Outcomes

#### MA2-5NA

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