1. Adding Integers
Chapter 11-3

2. Modeling Addition of Integers
To add integers, you can use counters or a number line to model integers.

3. Using Counters Color counters represent integers.
Red Counters=negative number
Yellow Counters=positive number
Positive 4=
Negative 3=
How do you think we would model zero?

4. ZERO Zero is a special number. You would use one red & one yellow.
This is called a zero pair!
Opposites cancel out—a red and a yellow erase each other!

5. You Try! Find each sum below using your counters. 1. 4 + 7 = 11= -6 = -9

6. Rule: When the signs are the same…
What do you do with the numbers?
Add
What will be the sign of your answer?
Keep the same sign

7. You Try! Example: 4 + -7= -3 1. 3 + -4= -1 2. 1 + -5= -4 3. 7 + -2 = 5
Find each sum using your counters. Zero Pairs cancel out! Look carefully at the example! = -1 = -4 = 5

8. Rule: When the signs are different…
What do you do with the numbers?
Subtract
What will be the sign of your answer?
The sign of the larger number!

9. Using a number line
You can use a number line to model the addition of integers.
You start at zero facing the positive direction.
You move forward for a positive integer.
You move backward for a negative integer.

10. Example Find 3 + (-2) using a number line.
Start at zero. Face the positive direction. Move forward 3 units for 3.
Then move backward 2 units for -2.
You stop at 1.

11. You Try! 1.) 4 + 2 = 6 2.) -2 + -4 = -6 3.) 1 + (-5) = -4

12. You Try!
Use counters, number line or your rules to solve the following:
A football team loses 3 yards on one play. On the next play, the team gains 2 yards. Find the result.
= -1
The result is a loss of 1 yard.