Example of Addition

How to add two-digit numbers (for example 30 + 40).

• First line up the numbers as per the place value (all the tens and the units lined up vertically). Put a line under the last number.

30
40

• Add the ones' place numbers. (0 + 0 = 0). Write the zero in the ones' place column.

30
40
 0

• Add the tens' place digits (3 + 4 = 7) and write the answer below the line in the tens' place column.

30
40
70

How to add two two-digit numbers (for example 54 + 42).

• First line up the numbers as per the place value (all the tens and the units lined up vertically). Put a line under the last number.

54
42

• Add the numbers in the ones' place digits (4 + 2 = 6).

54
42
 6

• Add the the tens' place digits(5 + 4 = 9) and write the answer below the line in tens' place column.

54
42
96

Adding three numbers (for example 5 + 3 + 9) involves two steps.

• First line up the numbers as per the place value (all the tens and the units lined up vertically). Put a line under the last number.
• Add the first two digits. (5 + 3 = 8). Hold '8' in your mind.
• Add the other digit to this sum. (8 + 9 = 17).

How to add three-digit numbers (for example 400 + 300).

• First line up the numbers as per the place value (all the hundreds,tens and the ones lined up vertically). Put a line under the last number.

400
300

• Add the numbers in the ones' place digits. (0 + 0 = 0) and write the answer below the line in the ones' place column.

400
300
  0

• Add the tens' place numbers (0 + 0 = 0) and place the answer below the line and to the tens' place column

 400
 300
  00

• Add the digits in the hundreds' place column (4+ 3 = 7) and write the answer below the line in the hundreds' place column.

  400
  300
  700

The addition facts for 0, 1 and 2 are in the following table.

When 0 is added to a second digit the answer is the second digit. (e.g. 0 + 6 = 6)

Adding 1 to any number is like counting up by 1.

Adding 2 to any number is like counting up by 2.

How to mentally add two two-digit numbers.

To add 73 and 34

• First add the digits in the ones' place(3 + 4)=7.
• Add digits in the tens' place(7 + 3) = 10.
• If the sum of ones's place numbers is single digit number then write the answer 107.

To add 65 and 87

• First add the digits in the ones' place(5 + 7)=12
• Add digits in the tens' place(6 + 8)=14
• If the sum of ones's place numbers is two-digit number then do the following
• Decrease the sum of ones's place by 10(12-10= 2)
• Increase the sum of tens' place by 1(14 + 1=15)
• Write the sums of tens and ones' place together to get the answer of 152

How to add two two-digit numbers (for example 35 + 78) with paper and pencil.

• First line up the numbers as per the place value (all the tens and the units lined up vertically). Put a line under the last number.

35
78

• Add the numbers in the ones' place. (5 + 8 = 13). This sum is a two-digit number so write 1 above the tens' place column and write the 3 below the line in the ones' place column.

1
35
78
 3

• Add the digits in the tens' place column (1 + 3 + 7 = 11) and write the answer below the line in the tens' place column.

 1
 35
 78
113

Here are the steps to add two-digit numbers (for example 67 + 89) using calculator

• Type the first number 67 by presing the 6 button and the 7 button
• Press + button
• Type the second number 89 by pressing the 8 button and the 9 button
• Press the = button to get the answer.

How to Estimate a sum by rounding.

• Round each two-digit number
• Add the rounded numbers to get the best estimate.

For example, estimate the following sums:

46 + 31, 64 + 25, and 45 + 34

46 + 31 = 50 + 30 = 80

64 + 25 = 60 + 30 = 90

45 + 34 = 50 + 30 = 80