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 2×3 matrices. The reason I do not start with 2×2 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 2×3 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.
Click Here to Download a Sample Set of Cards for the Activity: Adding and Subtracting Matrices – Using Rainbow Cards
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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