1. Aim: How Can We Add and Subtract Integers
Do Now: Identify each of the following as either counting number, whole number, integer, rational number, irrational number, or real number Π 5
0.75 -7

2. Rules for Adding Integers
When you are adding integers and the signs are the same (ex. Two positive signs/two negative signs):
You add and keep the given sign
Ex: = 11
= -7
When you are adding integers and the signs are different (ex. One positive sign and One negative sign):
You subtract and take the sign of the larger number
Ex: = -1
(9 – 8 = 1; Since the sign of the larger number is negative, the answer will be -1)

3. Let’s Try Some Together= = = = =

4. Rules For Subtracting Integers
When you are subtracting integers, use the rule KEEP CHANGE CHANGE
Keep the sign of the first number, Change the minus sign to an addition sign, Change the sign of the second number.
After you do KEEP CHANGE CHANGE, follow the rules for Adding Integers
Ex: 3 – (-4)
Keep Change Change: Keep sign of 1st #: 3
Change – to +, Change sign of 2nd #: -4 becomes 4
Follow Rules for Addition: = 7

5. Let’s Try Some Together
-8 – 4 =
5 – (-5) =
6 – (9) =
-7 – (-6) =

6. Working With Signed Numbers
Here is a Song to Help Us Remember the Rules For Adding & Subtracting Integers
Working With Signed Numbers
May be Sung to the Tune of “London Bridge”
When you’re adding integers, integers, integers
When you’re adding integers, follow the sign.
When the signs are different, different, different,
When the signs are different, you subtract.
Then the answer takes the sign, takes the sign, takes the sign
Then the answer takes the sign of the larger number.
When you’re subtracting integers, integers, integers
When you’re subtracting integers, use Keep Change Change.
Once you use Keep Change Change, Keep Change Change, Keep Change Change
Once you use Keep Change Change, follow the rules for addition.