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Contributor: Erika Wargo. Lesson ID: 12803
You already know how to add and subtract. Did you know that sometimes you have to add in order to subtract? Taking a large number from a smaller number is easier when you borrow tips from this lesson!
You might drive to a store, or you might borrow from your neighbor!
Subtraction is used to find the difference between two numbers.
You have probably learned that the larger number is usually the starting number in subtraction. Sometimes, you will need to regroup, or borrow, from another number before you can subtract.
Take a look at two phrases that will help you remember whether you need to regroup or not.
Just like with addition and subtraction of any number, start in the ones place.
More on the top? No need to stop!
Subtract 44 from 85.
| 8 | 5 | ||
| - | 4 | 4 | |
| 4 | 1 |
Look at the ones place. 5 is on the top, and 4 is below the 5. Since 5 is greater than 4, subtract and move to the tens place.
Look at the tens place. 8 is on top and 4 is below the 8. Since 8 is greater than 4, subtract straight down.
This problem did not need regrouping.
More on the floor? Go to the neighbor and borrow 10 more!
Subtract 58 from 73.
| 7 | 3 | ||
| - | 5 | 8 | |
Look at the ones place. 3 is on the top. 3 is smaller than 8, which is the number below it. You need to borrow from the tens place.
Borrowing from the tens place will add value to the ones place, without changing the overall value of the number.
Since you cannot subtract 8 from 3, you will need to borrow a 10 and add it to the ones place. The 7 tens become 6 tens, and the 3 ones become 13 ones.
We show this by adding 3 ones and 10 ones, which is 13 ones. You can see in the example below this is shown by placing a 1 in front of the value in the ones place. Now it is 13.
Now, you can subtract both place-value spots, starting with the ones.
| 6 | |||
| 7 | 13 | ||
| - | 5 | 8 | |
| 1 | 5 |
It is helpful if you can look at a subtraction problem and decide whether or not regrouping is needed.
If the value on the top is less than the value below it, you will need to regroup. You cannot take away more than what you start with.
No, because you only have $7!
Look at each of the problems below and decide whether or not they would need regrouping. (You do not need to solve them!)
Great! If not, watch the video below to review.
Continue on to the Got It? section to practice two-digit subtraction with regrouping.
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