Getting Interactive with the Common Core: Decomposing Numbers

I am always looking for fun, simple, interactive ways to do math with my kinders. I especially like activities that they can become independent at, but produce something so parents can see what we’ve been working and I can evaluate student progress. And, like my students, I am very tired of pages that require them to show what they know by coloring. COLORING IS BORING! Five year olds like to DO things, and by golly I am going to give them what they want!

So my students learned how to decompose numbers in a hands-on experience with unifix cubes, and then continued to develop the concept using 1″ squares of construction paper in a representation of the cubes. They glued the squares into decomposition patterns and recorded the corresponding addition sentences.

Four Different Sets of Decomposing Number activity pages are available for purchase in my TpT store

Shop Decomposing Numbers on TpT store

(And just in case you’re wondering – YES! I do use the word decompose when I tell my kiddos what we’re doing. I like for them to hear the grown up word for what they’re doing. So I sprinkle in the big vocabulary for the kids who love new words and also mix in some other expressions like, How else can you make 5? or What’s another way to build the number 8?)

But I digress. Back to this week’s math activities. I introduced the concept of breaking numbers into 2 parts using 2 colors (green and orange) of unifix cubes. I had cubes, and so did each students. Everyone also had a whiteboard and dry-erase marker. We started VERY simple.

Day 1: Introduce decomposition with Unifix cubes

Below is a summary of my dialogue with the students:

Ok everyone, I want you to hold up  5 green cubes that are all connected in a stick. Show me a stick of 5 green cubes. 

Great! Look at your cubes. How many green ones do you have? (5)  How many orange cubes are in your stick? (0)

I could write an adding sentence about my cubes! What would the adding sentence be for the green and orange cubes in my stick? (The answer is 5+0=5, which I recorded on my whiteboard after a student provided the equation.) 

Super! Now let’s trade one of our green cubes for an orange cube. Hold up a stick that still has 5 cubes, but now one of them is orange. Look at your cubes again. Now what would my adding sentence be? (4+1=0, which I also recorded)

We went through this entire process, continuing to swap one cube at a time until we reached 0 greens plus 5 orange. At which point, I asked the class to look at all of the sentences they told me and look for patterns. (Some numbers go up, some numbers go down, and the sum stays the same). We took a few minutes to discuss WHY those patterns happened.

Then we repeated the process using another set of cubes (3 greens, 0 orange). This time we traded cubes together and all of the students recorded the addition sentences on their personal boards too.

Day 2: Review Decomposition and Introduce Paper Activity

The following day we began with a quick review using 2 colors of cubes (blue and red) and our dry-erase materials. This time we decomposed the number 4. After recording the addition sentences, we took a few minutes to discuss patterns we observed. Now they were ready. I introduced their first decomposing activity page. We did Four Ways to Decompose 3 because it was a short activity and VERY familiar from the day before. The kids LOVED it!

Day 3 and Beyond: Move Toward Independent Practice

 We continued to discuss decomposition, but our discussion became quicker each day and the class was more eager to complete the activity with paper tiles. Next week I set the Decompose 2 worksheet in my lesson plans as a bellwork activity. I am completely confident in their ability to handle the activity independently.

We also use subtraction to decompose numbers in my classroom. Click here to read all about the experience.

Have a great day!