Adding Integers

The sums of integers can be placed in two categories: adding integers with the same signs (both positive or both negative) and adding integers with different signs (one positive and one negative).  Different rules apply depending on whether the addends have the same sign or not. 

Same signs

• 4 + 2 =  positive 4 plus positive 2
• (-4) + (-2) =  negative 4 plus negative 2

Add the absolute values of the numbers.  Then attach the sign of the addends.

Different Signs

• (-4) + 2 negative 4 plus positive 2
• 4 + (-2) positive 4 plus negative 2

Subtract the number with the smaller absolute value from the number with the larger absolute value. Then attach the sign of the addend with the larger absolute value.

Example

Add:  5 + (-12)

|5| = 5;  |-12| = 12
12 - 5 = 7
because |-12| > |5|, attach the negative sign.

5 + (-12) = -7

Practice 

Add each.

1.)  4 + (-8) 

 

 

 

 

2.)  12 + (-17) + (-18)

 

 

 

 

3.)  -6 + 7

 

 

 

 

4.)  -651 + (-231) + 524