You may never have used this word with your students, but guaranteed you have engaged in decomposing tasks. Here are some other phrases you may have used:
- Part-part-whole: if you are an intermediate teacher you may never have used this phrase. Many primary teachers do, however. When you work with part-part-whole ideas, you are also predicting value of a part if you know the whole and the other part used to make the whole.
- Expanding numbers: this is a particular kind of decomposing. Expanding describes the process of breaking a number up into place-value parts (325 = 300 + 20 + 5).
Decomposing breaking a number into parts any way that you like. So I can decompose 325 into 150 + 150 + 2 + 3 or any way that I like! This is a foundational number sense skill.
Click here to watch a great explanation by Christina Tondevald (Build Math Minds).
Here are some games and activities to practice decomposing:
- What’s in the cup? We recommend five frames (printout: Five Frames) be available for students as they play this game. This is a good game for early primary.
- Splat! by Steve Wyborney. These activities can be projected and used for whole class engagement. There are levels targeting early primary to intermediate.
- Shake and Spill: This is a simple game with a bunch of extensions (graphing is my favourite). Great for K-2.
- Part-Whole Triangles: This link takes you to a video explaining this great card game. A fun challenge for any level, although perfect for grades 1 and 2 (in terms of the numbers you work with).
Here is some adding practice that uses the concept of decomposing (Great for grades 2-4):
- Level 1 (adding to twenty): Make a 10 strategy (word); Make a 10 strategy (pdf)
- Level 2 (adding to 100): Make a friendly ten to add to 100 (word); Make a friendly ten to add to 100 (pdf)