Using Two Color Markers to Represent IntegersFeaturing the Marker Brothers

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Model Addition and Subtraction of Integers using Physical Materials.

We can use colored markers to represent integers when solving problems.

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When solving problems with integers, it is critical to model exactly what the problem instructs you to do.

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In this lesson, the red marker will represent a positive number and the yellow marker will represent a negative number.

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Let’s Model 3, -2 and 1

3-2

1

When you have the same amount of red markers as you do yellow, then these are called zero pairs.

The model represents 3 zero pairs.

-3 + 3 = 0

When using markers to model, be careful

to write only the amount you see.

When you have zero pairs, draw a line through the positive and negative markers to cross them out.

The model represents 3 zero pairs.

-3 + 3 = 0

Use a / to cross out your zero pairs.

Things to use as Modeling Mat:

1. Sheet of typing paper or notebook paper2. Small white board3. Sheet of white card stock

When solving addition or subtraction integer problems, use a modeling mat to model your problems on.

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Example 1: -2 + -3 = -5

When using markers to model, + means to

add to the mat.

Step 1: Model the first number.Step 2: The sign tells you to add -3.Step 3: Look at the set and record your answer.

Example 2: -2 - 1 = -3

When using markers to model, - means

take away from the mat.

Step 1: Model the first number.Step 2: The sign tells you to take away positive 1.Step 3: You don’t have positive 1 to take away, so you must add one zero pair.Step 4: Take away positive 1 .Step 5: Look at the set and record your answer.

Another Look at Example 2: -2 - 1 = -3

When using markers to model, be careful

to write only the amount you see.

A model of the -2 - 1 can also look like this:

Example 3: -2 - (-3) = 1

When using markers to model, use zero pairs to

add maekers to your mat when needed.

Step 1: Model the first number.Step 2: The sign tells you to take away negative 3.Step 3: You don’t have negative 3 to take away, so you must add one zero pair.Step 4: Take away negative 3 and you have your answer.

Closure• Step 1: Model the first number.• Step 2: The sign tells you what to do.• Step 3: If you don’t have enough counters to perform the operation, add

zero pairs.• Step 4: Review you set and record your answer.

Practice Time! Take out your workspace!

When using markers to model, be careful

to write only the amount you see.