3 Digit Addition
3digit addition is the addition of numbers where either one or all the addends are of 3 digits. We know that addition is an operation used in Math to get the sum of numbers. While the addition of onedigit numbers can be done mentally, the addition of 3 digit numbers needs to follow some rules. 3 digit addition can be done with regrouping or without regrouping using the basic rules of addition. Let us learn more about 3digit addition in this article.
1.  What is 3Digit Addition? 
2.  3Digit Addition Without Regrouping 
3.  ThreeDigit Addition With Regrouping 
4.  FAQs on 3Digit Addition 
What is 3Digit Addition?
In 3digit addition, we need to place the given numbers into columns according to their respective place values, like ones, tens, hundreds, thousands, and so on. The addition of 3digit numbers is similar to 2digit numbers where numbers can be added without regrouping (carrying) or with regrouping. It should be noted that the numbers that are being added are called addends and the answer that is obtained after adding these numbers is called their sum. Let us see the basic steps that are followed in 3digit addition.
 Step 1: Place the given numbers (addends) one below the other in such a way that they fall correctly under the columns of ones, tens, and hundreds.
 Step 2: Start adding the numbers from right to left beginning from the ones column, followed by the tens column and then the hundreds column.
 Step 3: After all the columns are added, we get the sum of the given numbers.
3Digit Addition Without Regrouping
While adding 3digit numbers, if the sum of any 2 digits is less than or equal to 9, we write the sum below the respective column and after all the columns are added, the answer is obtained. This is called addition without regrouping. For example, let us add the numbers 148 and 431 to see 3digit addition without regrouping.
Let us understand 3digit addition with the help of the following steps:
 Step 1: Add the numbers under the ones column. 8 + 1 = 9. Write the sum (9) in ones column.
 Step 2: Add the numbers under the tens column. 4 + 3 = 7. Write the sum (7) in the tens column.
 Step 3: Add the numbers under the hundreds column. 1 + 4 = 5. Write the sum (5) in the hundreds column.
Thus, the sum of the numbers 148 and 431 is 579.
ThreeDigit Addition With Regrouping
Regrouping is another name for carrying over. In the operation of addition, when the sum of the addends is greater than 9 in any of the columns, we regroup the numbers and carry over the extra digit to the preceding column. Let us understand this with the help of the following example, let us add 582 and 173.
Let us understand 3digit addition with regrouping using the following steps:
 Step 1: Add the numbers under the ones column. 2 + 3 = 5. Write 5 in ones column.
 Step 2: Add the numbers under the tens column. 8 + 7 = 15. Write 5 in the tens column and carry 1 to the hundreds column. We did this step because after adding 8 and 7 we get 15, but we cannot place 15 in the tens column because we can write just one digit below each column. So, we regroup the number 15. For this, we place the 5 in the tens column (corresponding column) and place the 1 on top of the hundreds column (the preceding column). In other words, when we get twodigit numbers as the sum, we place the ones digit in the corresponding column and we carry over the tens digit to the next column to the left. This carryover is added in that column where it is placed and the addition continues.
 Step 3: Add the numbers in the hundreds column. This means, 5 + 1 + 1 (carryover ) = 7. Here, after the carryover is placed in the hundreds column, it is added along with the other addends.
Thus, the sum of the numbers 582 and 173 is 755.
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3Digit Addition Examples

Example 1: Add the 3digit numbers: 623 + 215.
Solution:
Let us write the numbers one below the other and add them.
 Step 1: Add the numbers under the ones column. 3 + 5 = 8. Write 8 in ones column.
 Step 2: Add the numbers under the tens column. 2 + 1 = 3. Write 3 in the tens column.
 Step 3: Add the numbers under the hundreds column. 6 + 2 = 8. Write 8 in the hundreds column.
This was 3 digit addition without regrouping and the sum of the given numbers is 838.

Example 2: Perform 3digit addition on the given numbers: 537 + 365
Solution:
Let us place the numbers one below the other and add them.
 Step 1: Add the numbers under the ones column. 7 + 5 = 12. Write 2 in the ones column and carry 1 to the tens column.
 Step 2: Add the numbers under the tens column. 3 + 6 + 1 (carry over) = 10. Write 0 in the tens column and carry 1 to the hundreds column.
 Step 3: Add the numbers in the hundreds column. This means, 5 + 3 + 1 (carry over ) = 9.
This was 3 digit addition with regrouping and the sum of the given numbers is 902.

Example 3: State true or false with respect to 3digit addition.
a.) 101 + 202 = 303
b.) 202 + 807 = 909
Solution:
a.) True, 101 + 202 = 303
b.) False, 202 + 807 = 1009
FAQs on 3Digit Addition
What is 3Digit Addition in Math?
3digit addition is the addition of numbers where either one or all the addends are of 3 digits. 3 digit addition can be done with regrouping or without regrouping using the basic rules of addition. We usually use the column addition method to add 3 digit numbers, where we place the given addends one below the other according to their place values and start adding them, beginning from the ones column, then, moving on to the tens column and then the hundreds column.
What is 3Digit Addition With Regrouping?
Regrouping is another name for carrying over. In the addition operation, when the sum of the addends is greater than 9 in any of the columns, it is called regrouping or addition with carrying over. For example, let us add 487 and 143 and understand 3digit addition with regrouping using the following steps.
 Step 1: Place the given numbers one below the other according to their place values.
 Step 2: Add the numbers under the ones column. 7 + 3 = 10. Now, we cannot place '10' in ones column since we can write only one digit below each column, so we regroup the number 10. For this, we write 0 in ones column and carry 1 to the tens column. This 1 (carryover) will be added along with the numbers in the tens column.
 Step 3: Add the numbers in the tens column. This means, 8 + 4 + 1 (carryover) = 13. We will again regroup 13 and write 3 in the tens column and carry 1 to the hundreds column.
 Step 3: Add the numbers in the hundreds column. This means, 4 + 1 + 1 (carryover) = 6. Thus, the sum of the numbers 487 and 143 is 630.
How to do 3Digit Addition?
3digit addition is the addition of numbers in which any one addend or all the addends have 3 digits. We can add 3digit numbers by writing them into columns according to their place values. Then, we begin adding the numbers from the ones columns, moving on to the tens column, and then the hundreds column. For example, to add 342 + 123, we add the digits under the ones column (2 + 3 = 5). Then, we add the digits under the tens column (4 + 2 = 6). Then, we add the digits in the hundreds column, (3 + 1 = 4). So, the sum of the given numbers 342 and 123 is 465.
What is 3Digit Addition Without Carrying?
While adding 3digit numbers, if the sum of any 2 digits is less than or equal to 9, we write the sum below the respective column and after all the columns are added, the final answer is obtained. This is called addition without carrying or regrouping. For example, let us add the numbers 412 and 243 and see 3digit addition without regrouping.
 Step 1: Add the numbers under the ones column. 2 + 3 = 5. Write the sum (5) in ones column.
 Step 2: Add the numbers under the tens column. 1 + 4 = 5. Write the sum (5) in the tens column.
 Step 3: Add the numbers under the hundreds column. 4 + 2 = 6. Write the sum (6) in the hundreds column.
Thus, the sum of the 3digit numbers 412 and 243 without carrying, is 655.
What is 3Digit Addition and Subtraction with Regrouping?
In the operation of addition, regrouping is also known as carrying, while in subtraction, regrouping is known as borrowing. For example, in 3digit addition, sometimes the sum of two numbers is more than 9. In this case, we regroup the sum by carrying over the extra digit to the preceding column. For example, let us add 148 and 124.
 Step 1: Add the numbers under the ones column. 8 + 4 = 12. Now, we cannot place '12' in ones column because we can write only one digit below each column, so we regroup the number 12. For this, we write 2 in ones column and carry 1 to the tens column. This 1 (carryover) will be added along with the numbers in the tens column.
 Step 3: Add the numbers in the tens column. This means, 4 + 2 + 1 (carryover) = 7.
 Step 3: Add the numbers in the hundreds column. This means, 1 + 1 = 2. Thus, the sum of the numbers 148 and 124 is 272.
In case of 3digit subtraction, sometimes, a digit in the upper row is smaller than the digit in the lower row. In this case, we borrow a number from the preceding column so that the smaller minuend becomes bigger than the subtrahend. This is called regrouping or borrowing, For example, let us subtract 478 from 792.
 Step 1: Arrange the numbers according to their place value. Start subtracting the digits from ones place. We can see that 2 is smaller than 8. So, we will borrow 1 from the tens column which will make it 12. So, 12  8 = 4. This is known as regrouping or borrowing in subtraction. Now, we will write 4 under the ones column.
 Step 2: After giving 1 to the ones column in the previous step, the '9' in the tens column changes to 8. Now, let us subtract the digits at the tens place and write 1 under the tens column (8  7 = 1).
 Step 3: In the hundreds column, we will subtract 4 from 7 and write 3 in the column. (7  4 = 3). Thus, after subtracting the given numbers by regrouping, we get the difference as 314.
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