2-Digit Addition

2-digit addition is a simple form of addition in which numbers are placed according to their place value of ones and tens and then added. 2-digit addition can also be done mentally following some basic steps. Let us learn the basic steps of adding 2-digit numbers together.

2-digit addition is done by keeping in mind the place value of numbers. 2-digit numbers have the place value expressed as ones and tens. While adding 2 digits together, we arrange the numbers column-wise under the respective place values. This method helps in adding the digits one by one. 2-digit addition can be done with regrouping (carrying forward) and without regrouping (no carrying forward). The numbers that are being added are called addends and the answer that is obtained after adding these numbers is called their sum. Observe the figure given below which shows that 70 and 15 are the addends and 85 is the sum.

2-digit addition with regrouping is a method in which we regroup the given numbers due to a condition. The condition is that if the sum of the numbers in one column is more than 9, we carry forward the extra number to the next column. In the case of 2-digit numbers, regrouping starts from the ones column and we move to the left towards the tens column. Let us understand this with the help of an example.

Example: Add 59 and 23.

Solution: Let us add these numbers using the following steps.

• Step 1: Arrange the numbers or addends according to their place value, i.e., ones and tens column-wise. So, 9 and 3 will be placed under the ones column and 5 and 2 will come under the tens column.
• Step 2: Start adding the numbers from the right, i.e., the ones column and proceed towards the left, i.e., the tens column. Here, 9 + 3 = 12.
• Step 3: If the sum in the ones column is more than 9, we obtain a double-digit number. Taking the double-digit number, we place the ones digit under the ones column and the tens digit is carried forward or regrouped to the next column which is the tens column. Since 12 is greater than 9, we carry forward 1 to the tens column and write 2 as the sum in the ones column.
• Step 4: While adding the tens column, we include the number that was carried forward from the ones column. Hence we add 5 + 2 + 1 (carry-over) = 8.
• Step 5: Once both the columns are added, we obtain the final sum. After adding both the columns, we get 59 + 23 = 82.

2-digit addition without regrouping is the simplest form of addition. This method is used in daily life while shopping or doing any financial transaction. Here, when the sum is less than or equal to 9, we write the number under the respective place value column and do not carry forward any number to the next column. Let us understand this with an example using the following steps.

Example: Add 45 and 31.

Solution:

• Step 1: Arrange the addends according to their place value, i.e., ones and tens. So, 5 and 1 will be under the ones column and 4 and 3 will be placed under the tens column.
• Step 2: Start adding the numbers from right to left, i.e., from ones to tens. This means 5 + 1 = 6. Move on to the tens column, 4 + 3 = 7.
• Step 3: After adding both the columns we get, 45 + 31 = 76. Therefore, the sum is 76.

2-Digit Addition of Decimals

2-digit addition of decimals is similar to the regular addition of whole numbers. In decimals, numbers are written according to their place value and the decimal point. Addition is done from right to left and if the sum is more than 9, we carry forward the extra digit to the next column. The steps are the same as mentioned above. Let us understand double-digit addition of decimals with regrouping and without regrouping.

2-Digit Addition of Decimals With Regrouping

For decimals, we use the same steps as given above. Let us understand this with an example.

Example: Add 3.9 and 1.2

As we can see above, the sum of 3.9 and 1.2 is 5.1. Let us understand the working with the help of the steps given below.

• Step 1: Arrange 3.9 and 1.2 according to their place value, i.e., ones and tenths. 9 and 2 are placed under the tenths column and 3 and 1 are placed under the ones columns.
• Step 2: Start adding from the right. So, 9 + 2 = 11. Here, we carry forward 1 to the ones column and write the other 1 in the tenths column.
• Step 3: Add the numbers in the ones column along with the number that was carried forward. 3 + 1 + 1 = 5.
• Step 4: Once both the column numbers are added we obtain the final sum. Therefore, 3.9 + 1.2 = 5.1.

2-Digit Addition of Decimals Without Regrouping

For adding 2-digit decimal numbers without regrouping, we use the same method that is used for whole numbers. Let us understand this with an example

Example: Add 6.2 and 3.2

As we can see above, the sum of 6.2 and 3.2 is 9.4. Let us understand the procedure using the following steps.

• Step 1: Arrange 6.2 and 3.2 according to their place value, i.e., ones and tenths. While 2 and 2 are placed in the tenths column and 6 and 3 are placed in the ones columns.
• Step 2: Start adding from the right, and we get 2 + 2 = 4. Moving on to the next column, we get 6 + 3 = 9.
• Step 3: Once both the columns are added we obtain the final sum. Therefore, 6.2 + 3.2 = 9.4.

Note: While adding 2-digit numbers, the decimal point does not move and remains in the same position.

☛ Related Topics

• 2-Digit Subtraction
• 2-Digit Multiplication
• 3-Digit Addition
• 3-Digit Subtraction
• 3-Digit Multiplication
• 4-Digit Addition
• 4-Digit Subtraction
• Addition With Regrouping
• Addition and Subtraction of Decimals

What is 2-Digit Addition?

Two-digit addition is a simple form of addition in which numbers are placed according to their place value of ones and tens and then added. We start adding from right to left, that is, we start from the ones column and move on to the tens column. Once both the columns are added, we obtain the final sum.

How to do 2-Digit Addition without Regrouping?

2-digit addition without regrouping is done in a simple way. The following steps show the procedure of two-digit addition:

• Arrange the numbers column-wise according to their place value.
• Start adding from right to left, i.e., start from the ones column and then move on to the tens column.
• Once we add both the columns, we get the final sum.

For example: 16 + 10 = 26.

How to Teach 2-Digit Addition with Regrouping?

2-digit addition with regrouping can be taught using the following steps. Let us add 29 + 41 and understand the procedure using the following steps.

• Arrange the numbers according to the place values like ones, tens, hundreds, and so on.
• Start adding the numbers in the ones column. If the sum is more than 9, we carry forward the extra digit to the tens column and write the remaining number under the ones column. Here, the numbers in the ones column are: 9 + 1 = 10. Carry forward the number 1 to the tens columns.
• Start adding the tens column and include the number that was carried forward from the ones column. Adding the numbers in the tens column = 2 + 4 + 1 = 7
• Once the sum is obtained for both columns, we arrive at the final sum. Therefore, 29 + 41 = 70.

How to Do 2-Digit Addition of Decimals?

2-digit addition of decimals is performed in the same manner as 2-digit addition of whole numbers. The only point to be remembered is that the decimal point does not move away from the numbers and the addition is done like the usual addition. The numbers are placed as per their place values like ones, tens, hundreds, before the decimal, while tenths and hundredths are after the decimal point. For example: 7.5 + 2.4 = 9.9.

How do you Add 2-Digit Numbers Mentally?

To add 2-digit numbers mentally, we need to add the numbers separately. First, we add numbers in the ones column and then move on to the tens column. The steps for addition are the same as the usual addition but here we do the calculation in our minds. While carrying forward or regrouping, we keep that number in the mind and then add.

In what Grade do you Learn Double-Digit Addition?

Double-digit addition is usually learnt in grade one, where the students learn single-digit addition and double-digit addition.