4th Grade Adding and Subtracting Multi-Digit Numbers Lesson (Free PDF)
To add or subtract multi-digit numbers, line up the digits by place value and work from the ones place to the left. Carry when a column adds to 10 or more. Regroup when a top digit is too small to subtract from. Check by using the opposite operation.
Grade 4 · Common Core State Standards: 4.NBT.B.4
- Always line up the digits by place value before you add or subtract.
- Start at the ones place and work to the left.
- Carry 1 to the next place when a column sum is 10 or more.
- Regroup 1 from the next place when the top digit is smaller; a 0 becomes 9 after regrouping across it.
- Check subtraction by adding, and check addition by subtracting.
How do you add multi-digit numbers?
The standard algorithm lines up the digits by place value and works one place at a time. It always starts at the ones.
- Line up the digits by place value.
- Add the ones. If the sum is 10 or more, write the ones digit and carry the tens digit.
- Move left one place at a time, adding the carried digit too.
In the example, \(5 + 9 = 14\), so write 4 and carry 1. The carry shows up four times, and the final sum is \(65,334\).
How do you subtract with regrouping?
Subtract from the ones place first. When the top digit is smaller than the bottom digit, regroup: take 1 from the next place to the left and add 10 to the place you are working on.
What do you do when there are zeros?
Zeros cannot give anything away, so look left until you find a digit that can. Each zero in between becomes 9 and the ones place gets 10 more.
Example: \(7{,}002 – 3{,}458\). After regrouping, subtract each place: \(12 – 8 = 4\), \(9 – 5 = 4\), \(9 – 4 = 5\), and \(6 – 3 = 3\). The answer is \(3,544\).
How can you check your answer?
Addition and subtraction undo each other. To check a subtraction, add the answer to the number you subtracted. You should get the starting number back. To check an addition, subtract one addend from the sum.
Here, \(33{,}587 + 18{,}759 = 52{,}346\), so the subtraction \(52{,}346 – 18{,}759 = 33{,}587\) is correct.
Questions about adding and subtracting multi-digit numbers
What is the standard algorithm for addition?
Write the numbers in a column with the places lined up. Add the ones first, carry when a column is 10 or more, and move left one place at a time.
How do you subtract when there are zeros in the top number?
Look to the left for the first digit that is not zero and take 1 from it. Each zero in between becomes 9, and the ones place gets 10 more. For 7,002 you get 6 thousands, 9 hundreds, 9 tens, and 12 ones.
What does regrouping mean?
Regrouping means trading 1 from a place for 10 in the place to its right. For example, 1 thousand becomes 10 hundreds, so 5,000 can be thought of as 4 thousands and 10 hundreds.
How do you check a subtraction answer?
Add the difference to the number you subtracted. If you get the starting number, the answer is correct. For 9,106 – 4,879 = 4,227, add 4,227 + 4,879 = 9,106.
Can you add numbers with different numbers of digits?
Yes. Line up the ones place, not the left edge. Write 0 or leave a blank in the empty places, and add column by column from the right.
All Grade 4 chapters: Grade 4 math.
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