Add and Subtract Integers

The sixth grade is working on adding and subtracting integers. We decided to "model" our work by showing how to add and subtract an integer using different color chips.

For example, Ashley wants to solve this problem.

5 + - 7

(5 add negative 7)

The first step Ashley will do is to get two different colors of chips. She has chosen white chips to represent the positive integers and red chips to represent the negative integers.

Now she will place 5 positive (white) chips on the table.

The 5 white chips represent the integer 5.

Now, Ashley needs to show how she is going to add a negative 7. How will she do this? She will add seven negative chips to the 5 positive chips. The negative chips are red.

Now Ashley can solve the problem 5 + -7. Do you know the answer? How can Ashley show the answer using chips?

First of all, Ashley must remove all the "zero pairs" in her model. A zero pair is a positive and negative chip whose sum is zero. Watch as she removes all the zero pairs.

It looks like she has removed 3 sets of zero pairs and she has two more sets to remove. Why did she remove the zero pairs? If you think it is because they equal zero, you are right! So, what will be left? What is 5 + -7?

What do the two red chips represent? Did you say negative 2? That is correct.

Now let’s subtract integers.

5 - (- 7)

(5 subtract negative seven)

Mike is going to show us how to subtract integers. Mike decides to use blue chips for positive integers and yellow chips for negative integers.

Now the first step is to place 5 blue chips on the table. (Did Mike choose yellow and blue because those are Onekama’s colors?)

Mike wants to subtract a negative 7. Do you see a negative 7 on the table? Where is he going to get a negative seven so he can take it away?

Mike decides to put in 7 yellow negative chips and 7 more blue positive chips. Why does he decide to add more blue chips? Do you remember the "zero pairs"? Mike adds 7 negative chips so he can take them away, but he cannot change the value of the 5 positive chips he started out with in the beginning. So if you look at the picture below, you will see that Mike still has a positive 5 on the table. He also, has a negative seven he can subtract.

Now, what must Mike do to solve 5 — (-7)? Mike will take the 7 negative yellow chips away. What is left?

We want to thank Mike and Ashley for showing us how to add and subtract integers. GREAT JOB!