LESSON: Operations with Whole Numbers

READ: Subtracting Whole Numbers

Subtracting Whole Numbers

Subtraction is the opposite of addition.

This means that if you can add two numbers and get a total, then you can subtract one of those numbers from that total and end up where you started.

When you add two numbers you get a total (or sum), when you subtract two numbers, you get the difference.

Example

$15-9=\underline{\;\;\;\;\;\;\;\;\;\;}$

This is a pretty simple example. You have fifteen of something and if you take away nine, then what is the result? First, we need to rewrite the problem vertically, just like we did when we were adding numbers. Remember to line up the digits according to place value.

$15\ \underline{ - \ 9}\ 6$

What about if you had more digits?

Example

$12, 456 - 237 = \underline{\;\;\;\;\;\;\;\;\;}$

Our first step is to line up these digits according to place value.Let’s look at what this will look like in our place value chart.

*Ten Thousands*	*Thousands*	*Hundreds*	*Tens*	*Ones*
1	2	4	5	6
		2	3	7

This problem is now written vertically. We can go ahead and subtract.

$12,456\ \underline{ \ - \ \ 237}$

To successfully subtract these two values, we are going to need to regroup. What does it mean to regroup? When we regroup we borrow to make our subtraction easier.

Look at the ones column of the example.
We can’t take 7 from 6, so we borrow from the next number.
The next number is in the tens column, so we can “borrow a 10” to subtract.
If we borrow 10, that makes the 5 into a 4.
We can make the 6 into 16 because $10 + 6 = 16$ . There’s the 10 we borrowed.

Be careful-be sure you subtract according to place value. Don’t let the regrouping mix you up.