For subtracting, I'm torn. It is not the way my mind thinks about integers. But in an effort to avoid putting my preferences on my students, I wanted to make an effort to teach it this way in case it helps some of my students "see" what is going on with subtracting.
It works like this:
Pink = Negative and Blue = Positive
If I have a problem such as -4 - 3…
Start with 4 pink chips to represent -4:
We want to subtract positive 3. There are not 3 blue chips available… so add 3 zeros (a pair of a positive and negative). We can do this because adding zeros does not change the value.
You are left with 7 pink chips, which equals -7.
I have to say that some students are doing really well with this model. However, I have some students getting pretty confused. You can see some of their thinking on their math blogs.
I plan to also show them how to use a number line to add and subtract as well. Does anyone have experiences with subtracting with the chip model? How did it go for you?