# Using a Number Line to Add and Subtract (Mathematics Lesson)

# How to Add Numbers on a Number Line

Adding a number is equivalent to moving that number of spaces to the right on a number line.**Question**: What is 4 + 3?

Step 1

Step 2

The solution to 4 + 3 is 7.

# How to Subtract Numbers on a Number Line

Subtracting a number is equivalent to moving that number of spaces to the left on a number line.**Question**: What is 6 - 2?

Step 1

Step 2

The solution to 6 - 2 is 4.

# How to Both Add and Subtract Numbers on a Number Line

The slider below shows an example of using a number line to both add and subtract numbers:##### Interactive Test

**show**

##### Top Tip

**ADDING & SUBTRACTING**

**Adding**is equivalent to going

**right**on a number line.

**Subtracting**is equivalent to going

**left**on a number line.

##### Note

# ORDER OF ADDING OR SUBTRACTING

Solving 3 - 2 is equivalent to starting at 3 on a number line and moving 2 places left:The solution is 3 - 2 = 1.

3 - 2 can be rearranged to (-2) + 3.

This is equivalent to starting at -2 on a number line and moving 3 places to the right:

Similarly, it can be seen that 1 + 2 gives the same answer as 2 + 1:

This is the

*commutative*property of addition - you can change the order of the numbers around the sign and still get the same answer.