# Adding integers with the same sign using models

## Lesson # 2: Adding integers (with the same sign)

#### Objectives

- Understand how to use models to add integers with the same sign
- Evaluate integer addition problems using mental math
- Develop methods for using integer tiles
- Develop real life situations that model expressions

#### Warm-Up

- State the definition of an integer and give three examples.
- Use integer tiles to add the following integers:

- - 8 + 3
- -6 + 6
- 13 + -8

#### Adding integers with the same (negative) sign

We want to use integer tiles again to add integers that have the same sign. So, both numbers are negative or both numbers are positive.

Let’s start with adding two negative numbers. Use your integer tiles to represent the expression...

Steps

- 1. Arrange your integer tiles.

- 2. How many zero pairs can we make? Zero Pair Answer

- 3. What is the answer to -8 + -6? -8 + -6 Answer

Use your integer tiles to represent:

- 4. -4 + -5

- 5. Can you do -20 + -15 without using your integer tiles? -20 + -15 Answer
- Question: What is the “sign” (positive or negative) before the number 15 in question #5? Answer to sign of number 15

When you are adding numbers with the same sign, what are you really doing? Answer

Can you think of a real life situation with your bank account that can represent adding to negative integers? Share here

#### Adding Integers with the same (positive) sign

You already know how to do this!

- 6. ) 4 + 8 = 12

- 7. ) 19 + 25= 44

- 8. ) 25 + 18 + 30 = 73
- Question: What is the “sign” (positive or negative) before the number 30 in question #8? Answer to sign of number 30

Here are the “rules” for adding integers with the same or different signs. Don’t memorize them! These should be used to help you explain your method.

- Let's use some mental math! Solve the following problems using mental math...

- -8 + -9
- -15 + -6
- 50 + 36
- -200 + -50

Answers to mental math problems

#### Assessment

Try out these websites to practice all of your new skills for adding integers with the same and different signs.

Share one thing you have learned on this wiki page from Lesson # 2.

- 1. Adding integers with different signs using models
- 3. Subtracting integers using models
- 4. Multiplying integers using models