1. Distributive Property--We all know that this is an important concept moving forward, but it can sometimes be tricky for students to wrap their minds around. I use lots of different strategies to help kids understand the distributive property, but the area model is definitely one of them.
The representation below can be seen as two rectangles, a 5 x 8 with an area of 40 and a 5 x 12 with an area of 60. Or you can see this as one rectangle, a 5 x 20 with an area of 100. This is a concept that is understandable for students, and it is a good way to reinforce our abstract ways of showing this concept.
Learning abstract representations of math can be one of the major challenges as students transition from elementary to secondary math, so connections like these can be helpful.
2. Factoring--This is the natural extension of using area model to teach distributive property. By simply leaving out the shared side length, we encourage students to factor, and help them see the connection between factoring and the distributive property.
It's good to start with an example that only shares one common factor, like this one.
Students can see that the side length has to be the same number. Next, we want them to make the connection between the same side length and a common factor of 35 and 56. Student thinking might be like this:
What 5 times what equals 35? 8 times what equals 56?
Finally, we want to students to make connections between the picture and the to the abstract work:
35 + 56 = 7(5 + 8).
Now, you can move to examples that have more than one common factor that could be factored out.
40 + 60 = 5(8 + 12).
Connecting the drawing back to the work is important....where do you find the 40, the 5, the 8, and so on in the picture?
3. Battling Common Misconceptions--If you give your students the problems (8)(4.5), would you be surprised to have some students give the answer of 32.5? Me neither! But the area model can again help us out.
If students have been using area model to show the distributive property, this representation should be familiar. This shows that the area is 36 and gives a visual illustration of why we can't multiply 8 x 4 to get 32 and simply add 0.5.
4. Reinforce proportional thinking--If I had to pick one topic that was the most important thing we do in middle school, it would be proportional reasoning. Every chance I get, every way I get, I want to reinforce proportional reasoning with my students. I want to give them different ways to see it. So what about this?
Since the side of 3 is the same for both rectangles, if you double the 4 to get 8, it also doubles the area from 12 to 24.
5. Move towards algebraic thinking--Ultimately, our middle school students need to be ready for the demands of algebraic thinking. The area model can also give us another way to get students using variables in middle school. Consider the progression of the examples shown below.
If students are consistently using the area model as a representation in our middle school classrooms, hopefully the jump to the last two representations will be easier.
So we've looked at multiplication charts and area model...what other elementary models and tools can continue to be helpful in middle school?