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How to Subtract Numbers Up to Three Digits

Instructor: Sabrina Hairston

Sabrina has taught a variety of subjects and grades as a substitute teacher and will complete her MAT in 2016.

This lesson will teach you how to subtract numbers up to three digits. Try some practical examples with only three short steps to follow in order to ensure success when subtracting.

Why Subtraction Is Important

Subtraction is an important skill because it tells us what we have left over after taking something away. We use subtraction often when dealing with everyday things like temperature, money, and measurements.

To learn how to subtract numbers up to three digits, let's look at an example of a problem that uses subtraction and deals with distance.

Subtraction and Distance

Mr. Superfly is looking to earn a free trip to Hawaii with the frequent flyer miles he has saved up from all of his business trips. He needs a total of 170 miles in order to earn the trip. He has already accumulated 63 miles. How many more miles does Mr. Superfly need to earn the trip?

Line it Up

In order to solve our distance problem, the first thing we need to do is make sure we line the numbers in our problem up correctly. The rule is that the ones place is on the far right, the tens place is in the middle, and the hundreds place is on the left. Let's see this in action.

Our example tells us that Mr. Superfly needs a total of 170 miles, and it says that he has 63. In order to find out how many miles he still needs we are going to subtract 63 from 170. When we line up our problem correctly it will look like this:


170-63


Borrow When Needed

The next step in our subtraction problem is to borrow. When you subtract, always start on the right (ones place) and move left. The ones place for our example tells us to subtract 3 from 0. Since we can't take 3 away from 0, we need to borrow from the neighbor to the left. The neighbor on the left here is the 7 (in the tens place). In order to borrow from the 7, we will strike through the 7 and turn it into a 6. The ten we borrowed will now go to the ones place, making the 0 a 10.


170 borrowing


Solve

Now that we have added a ten to the 0, we can complete our last step for the ones place: solve. 10 - 3 = 7. The answer for our ones place is 7.

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