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 stores Teachers Pay Teachers and Teachers Notebook.
Shop Decomposing Numbers on Teachers Pay Teachers
Shop Decomposing Numbers on Teachers Notebook
(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)
|List all the ways to Decompose 5|
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.