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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
Find 4 on the number line.



Step 2
Move 3 to the right.



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
Find 6 on the number line.



Step 2
Move 2 to the left.



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
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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.