This is the most important lesson in the Unit on Matrices! The easiest way to teach adding and subtracting matrices is by color coding.

Let's Start Adding and Subtracting Matrices

I start with adding two 2x3 matrices. The reason I do not start with 2x2 matrices is because it is easier to show them that the matrices must be the same size to add or subtract them.

The other reason I use 2x3 matrices is because that means there will be 6 numbers inside each and there are 6 colors to the rainbow (I know that's debatable but for the sake of the lesson go with it).

Red - Orange - Yellow - Green - Blue - Purple

Each number from the first matrix gets matched with its Corresponding number in the second matrix. Then they are added or subtracted. I do this with a group activity.

Cards like the ones below are passed out to small groups and they find the solutions. The rest of the activity is available if you are a Algebra 2 Teacher Community Member:Click here to Join Now!

Here are two cards I use to introduce the lesson...

I always start with addition. Simply because it is easier.

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Adding and Subtracting Matrices Word Docs & PowerPoints

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