Wednesday, March 2, 2016

Lesson Idea: Combining Like Terms

I haven't written about a lesson idea in a while!

While talking with an 8th grade teacher today, I was reminded of a lesson I've done in the past about combining like terms. I wanted to write a quick post to share and also so that I can have it saved to refer back to.

The lesson begins by showing this clip:

The kids always laugh and enjoy the silliness of it. When it keeps going, I hear a lot of "You gotta be kidding me!" and "ugh, how long is this going to go on?" Perfect. I feel like I'm creating the controversy (create the controversy, Dan Meyer suggests is a first step)

After the video, I talk about a simpler version of this same idea.

Me: What if I ordered 5 hamburgers, 3 orders of fries, 6 hamburgers, and 2 more orders of fries. Is there a better way to order that is less confusing?

Students: Yes! (they are almost frustrated with me!) Put the hamburgers together and the fries together.

Me: Oh, so if I wrote ((write on the board: 5h + 3 f + 6h + 2f)), how would it look if I combine them? ((notice I start using the word COMBINE))

Students: Yes! 11h and 5f!

Me: ((I record on the board. 11h + 5f)) Like this?

Students: ((now wondering how I have a job as a math teacher if I'm having this much trouble. I love playing to this and creating the headache for students! Make them do the thinking!))  Yes!!!

Me: So the coefficient of 11 means I have 11 h's and the coefficient 3 means I have 5 fries? ((start using the vocab that you want students to know. Using context clues, students start to realize what I mean by the word))

I go on to show other situations and move towards using x and y. Also pose questions that include subtraction. Also, asking, "what if there was a negative coefficient?"

I would love to hear how you imagine using this clip to introduce combining like terms!

**Postscript: The idea using this video with a combining like terms lesson was not original to me. I found it online a few years ago. I can't find the original source of the idea. Was it a blog? A website? I can't remember. I also don't remember how the original poster suggested using it. However, send me a note or tweet if you know where this idea was first suggested. It certainly is a creative idea and worth "stealing," as all good teachers do! :)


  1. Great idea! Love the"hook" at the beginning to get students engaged!

  2. I would love to use this, but the clip will not work! Do you have the direct link?

    1. Try this:
      Let me know how it goes if you use it in your classroom! :)

  3. I LOVE THIS LESSON! Pulling kids into the lesson (with something so annoying) and making a real connection with math!!!

  4. Nice job! While some kids will thrive if we just give them a messy example, my experience say that your hook is much more impressionable. I suspect you later referred to the fast-food order many times later (a 2-second reminder). "Messy example" would not likely be so quick.

  5. Thank you so much for this! I am going to use it in an 8th grade unit where some students struggle to see why simplifying expressions is important. I am also going to make one small change: Instead of asking how to represent an order of 5 hamburgers, 3 orders of fries, 6 hamburgers, and 2 more orders of fries, I will ask how to represent the COST of 5 hamburgers, 3 orders of fries, 6 hamburgers, and 2 more orders of fries with h and f representing the cost of those items. I worry that without that clarification it might fuel the misconception some students have that a variable is an abbreviation for a word instead of representing a value for a number (which causes students to think that 4Q=1G). Again thank you so much for this I know the students are going to love it.