Adding and Substracting Using Number Line

• Add a positive integer by moving to the right on the number line
• Add a negative integer by moving to the left on the number line
•   Subtract an integer by adding its opposite
•  To add integers having the same sign, keep the same sign and add the absolute value of each number.
•  To add integers with different signs, keep the sign of the number with the largest absolute value and subtract the smallest absolute value from the largest.
•  Subtract an integer by adding its opposite.

 Formula

Examples:

Adding

• 3 + 4 =?  

           Start at positive three on the number line and move four units to the right, you end up at positive seven.

      
           3 + 4 = 7 

•  -3 + (-4) =?

           Start at negative three on the number line and move four units to the left, you end up at negative seven.

            -3 + (-4) = -7

•  3 + (-4) =?

           Start at positive three on the number line and move four units to the left, you end up at negative one.

           3 + (-4) = -1

•  -3 + 4 =?
  

           Start at negative three on the number line and move four units to the right, you end up at positive one.

           -3 + 4 = 1

Substracting

• 3 - 4 =?
  

          Start at positive three on the number line and move four units to the left, you end up at negative one.

          3 - 4 = -1

• -3 - (-4) =?

          Start at negative three on the number line and move four units to the right, you end up at positive one.

              -3 - (-4) = 1

• 3 - (-4) =?

          Start at positive three on the number line and move four units to the right, you end up at positive seven.

 

           3 - (-4) = 7

• -3 - 4 =?

          Start at negative three on the number line and move four units to the left, you end up at negative seven.

          -3 - 4 = -7