Lesson 4: Combining Integers

AIM: How do we combine positive and negative integers?

​Start up:

​Arnold borrowed $500 each week for 3 weeks from his cousin.

He earns $12 an hour and works 40 hours a week.

How many weeks of work will is take Arnold to pay back his cousin?

Multiple Select

Your turn! What are integers? Choose all that apply.

• Whole Numbers

• Zero

• Negative Numbers

• Positive Numbers

​Rules for Combining Integers: Adding

​

• ​Same signs? Add and keep the sign

​

-5 + -2 = -7

8 + 12 = 20

​

• ​Different signs? Subtract and keep sign of whatever you have more of (sign of number with largest absolute value)

​

-10 + 3 = -7

15 + -5 = 10

​

​​Rules for Combining Integers: Subtracting

​

• ​Subtracting a positive = adding a negative

​

​7 - 2 = 7 + -2 = 5

​

• ​Subtracting a negative = adding a positive

​

​7 - (-2) = 7 + 2 = 9

How to change subtraction to addition: Keep Change Opposite (KCO)

​

K C O

7  -  2

7  + -2

Keep 7

Change subtraction to addition

Opposite of 2 is -2​

​Class Work:

​

​1. Mild (did you get 2 or more wrong? Start here)

​2. Medium (1 wrong? Start here)

​3. Spicy (0 wrong? Start here)

​Finish Line

​

​10 + -15

​

-8 + 5

-17 - (-5)