Using a Number Line to Add and Subtract (Mathematics Lesson)
How to Add Numbers on a Number LineAdding a number is equivalent to moving that number of spaces to the right on a number line.
Question: What is 4 + 3?
The solution to 4 + 3 is 7.
How to Subtract Numbers on a Number LineSubtracting a number is equivalent to moving that number of spaces to the left on a number line.
Question: What is 6 - 2?
The solution to 6 - 2 is 4.
How to Both Add and Subtract Numbers on a Number LineThe slider below shows an example of using a number line to both add and subtract numbers:
Top TipADDING & SUBTRACTING
Adding is equivalent to going right on a number line.
Subtracting is equivalent to going left on a number line.
ORDER OF ADDING OR SUBTRACTINGSolving 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.