Category Archives: #CCSS

Last year I used the process of Claim-Evidence-Reasoning, or CER, to teach statistics. I wrote about it a lot. I mean a lot. Seriously. More than I’ve written about anything else. (two more posts here & here.) But that was about teaching statistics. This term I have a geometry class and as my students were struggling with a proof, I had an “aha!” moment. Why not use the claim-evidence-reasoning process?

We were trying to prove why the sum of the interior angles of a triangle equals 180 degrees. Here’s what I gave them to start with.

That’s right. I just gave them a triangle. The traditional way to approach this proof is to draw a line through point C so that it’s parallel to side AB. And I did include that on the back, in case kids got stuck. But here’s the interesting thing – faced with just the triangle and a background of transformational geometry, they began rotating this triangle to tessellate a line of three triangles. It looked like this:

Then I asked kids to think about this approach, talk about it with each other, and then write a proof for why the sum of the interior angles of a triangle equals 180 degrees.

I collected what everyone had written and, like before, transcribed it for students to analyze for evidence and reasoning. Then we reviewed as a class to try to sort out the evidence (highlighted in cyan) from the reasoning (highlighted in orange). From there, I was able to give them another try with some direction from our conversation about evidence and reasoning. This was more successful. I pulled 4 examples to share with the class – I could have easily shared twice that number, which was more than half of the papers that I received from the class of 22. Here’s one of the 4 examples:

Unfortunately, what you can’t seen in this scan is how the individual statements are numbered. Thinking doesn’t always come in deductive order. Sometimes you just have to write down what you know and why you know it. Then you can go back and organize it. It’s like making a rough draft of the proof.

Today, as we were reviewing these exemplars, I asked my students how often they wrote rough drafts for their humanities essays (all the time) or how often they wrote rough drafts of their science CER (claim-evidence-reasoning) papers (all the time). So, it shouldn’t be surprising that a rough draft might be in order for a geometry proof.

In this fourth entry about using structure to teach algebra, I’d like to focus on how we moved our kids from the picture-based systems to using traditional symbols. We focused on systems of two equations because even though they could solve systems involving more than two equations using emojis and mobiles, moving to traditional symbols could be more intense.

We began with systems that could have been represented by mobiles.

Many students even drew their own mobiles using x’s and y’s. Others went right to the equation 2x + 5y = 4x + 2y and came up with 3y = 2x. Again, they used this relationship as a direct substitution. Some substituted into the top equation to get 3y + 5y = 48, while others transformed the bottom equation into 6y + 2y = 48. Once they were able to solve for y, they were able to solve for x.

But we didn’t just want systems that immediately transformed into mobiles, so we also gave them ones like this:

We were quite curious about what they would do with this kind of system. Our instinct and experience would be to solve the bottom equation for y, but that’s not what the kids did. They added 3 to both sides of the bottom equation so that both equations were equal to 22. This left them with the equation 2x + 3y = 3x + y + 3, or 2y = x + 3. There’s no direct substitution here, though, so kids needed to reason further. Some used y = 0.5x + 1.5 while others said that x = 2y – 3, which led them to 2x = 4y – 6. Again, they did this on their own, without any direct teaching from us.

We also gave them systems like this one, which seemed pretty obvious to us:

Just about every student was able to come up with the equation 3x – 2 = 4x + 1, but lots of kids weren’t sure what to do next because the equation didn’t contain x & y. Those students needed a bit of prompting until they realized that they could use that equation to solve for x.

And then there was this one:

It doesn’t look all that different from the others. Most students added 24 to the bottom equation and proceeded as above. But I had one student who decided to multiply the bottom equation by -5. What?! When I asked him why he decided to multiply, he said that he wanted to make the bottom equation equal 20 and multiplying by -5 would do that. Fair enough.

The entire journey, from emoji’s to mobiles to traditional symbols took us to a completely different substitution method for solving systems. Had we not been open to following our students’ lead, we never would have learned these ideas that were completely intuitive to them. Remember, these weren’t “honors” kids, but they were willing to try, to think, and to take risks. And we gave them the space and time to play with the ideas.

The October 2017 issue of Mathematics Teacher included the article “An Emoji is Worth a Thousand Variables,” by Tony McCaffrey and Percival G. Matthews. (Note that you need to be an NCTM member to access the article without purchasing it.) The authors introduced their students to systems by using sets of equations comprised of emojis, similar to those puzzles that are found on Facebook. Lots of people, including those who say they hate math or they aren’t good at math or, “I’m not a math person” will do puzzles like these. They get lots of likes, answers posted in the comments, and shares –  probably because this doesn’t look much like math. Take a moment and solve the puzzle.

What if, instead of the emoji puzzle, I had posted this puzzle:

The two are actually equivalent, but the abstract nature of the second representation is enough to make our students who see themselves as not math people shut down.

My fall term teaching partner and I used the emoji approach with our students. We hadn’t discovered the website yet, so we gave our students this short worksheet. Many of our students had struggled with math prior to coming to Baxter Academy. They were in self-contained or pull-out special education settings or in pre-algebra classes in middle school. A few probably had something closer to algebra 1, but they certainly hadn’t solved systems of three or more equations. They had no problems understanding what the emoji puzzles were asking of them. They weren’t put off by the number of equations or the number of icons. They were able to explain their solution process clearly and with great detail.

In a follow-up exercise, asking students to make connections between the emoji representation and the more traditional representation, nearly 80% of my students saw and could articulate the direct connection between the icons and the variables.

If the emoji system is more engaging and more accessible, then why don’t we use more of them to introduce systems of equations? Is it because emoji systems seem to “dumb down” the mathematics? The authors of the article make the case against that view:

“The algebra represented in [the emoji system] is not dumbed down at all. Notice that the puzzle presents a linear system in three variables … First-year algebra students are generally not exposed to three-variable systems; indeed, when McCaffrey checked all the first-year algebra texts in his school’s faculty library, none included systems of three variables. Although McCaffrey’s students had never seen three-variable systems before this class, most found the puzzle intuitive enough to solve.”

It is important to transition from emojis to more formal algebra, but it’s not important to start with the most abstract representation – the one that leaves too many of our students behind.