Charge! v2 – Activity Makeover

Background. I’ll share an activity. Offer some ideas on what’s wrong. Invite you to share your own diagnosis/treatment. Then (end of week) share an upgraded version of the activity. (More details about this series are available here.)

Several Mondays ago, I shared the Desmos Activity Builder version of Charge!, a linear modeling task where students predict how long it will take for a phone to become fully charged. Here’s the diagnosis.

In that post I suggested that the Activity Builder version of this activity was inferior to its original slide-deck-driven version, in part because it struggles with these principles from the Desmos activity building code:

  • #5 – Give students opportunities to be right and wrong in different, interesting ways.
  • #8 – Create objects that promote mathematical conversations between teachers and students.

Featured Comments

Dave Johnston: “Can we give students more chucks of the data and give them an opportunity to revise their model? What if different groups of students had different data points along the way & they discussed the models they came up with?”

Nathan Kraft: “I’m trying to figure out what Desmos adds to the activity… This activity pigeonholes students into one way of doing it, and even for students in higher grades, I’d like to give that option to explore it differently… In the end, maybe this doesn’t work in activity builder.”

Elizabeth Raskin: “One of the beautiful things about 3 acts is allowing students to determine what information is important (to an extent) and what to do with it.”

Mark Kreie: “Utilizing the Classroom Conversation Toolkit w/ teacher pacing and pausing might be a benefit to this activity.”

My Upgrade

I find myself wondering what several commenters suggested: maybe the best version of this task doesn’t live in Activity Builder. I’m definitely open to that possibility.

That being said, I still wanted to see how far forward I could push the AB version.

I recommend opening up Charge! v2 while you read through the rest of the post. Here is what’s new:

  1. Fresh artwork, all throughout, including a video reveal. This doesn’t shift the pedagogy, or address the weaknesses above, but it adds a little polish to the existing structure. And when it comes to the video, that adds a little anticipation, which is often a good thing in a math classroom.
  2. Condensed opening. I love asking students “what do you notice/wonder?” But I haven’t figured out how to open an Activity Builder activity with that approach. So I’ve trimmed the opening to make room for more discussion later on, a la Principle #8 (“Create objects that promote conversations…”).
  3. “Informalized” the sketch on Screen 2. Goodbye axis scale. Goodbye grid. Goodbye sample data points. Hello increased variety of student responses. That’s the plan, anyway. I’m anticipating an uptick in variety here, ranging from type of graph (linear vs nonlinear) to features of specific sketches (e.g., steepness, starting point). And that could lead to some nice interplay between Principle #5 and Principle #8.
  4. Condensed middle. The core here is much tighter. It’s now: Build a model. Use the model. Interpret your model. This condensing improves our conversation-to-screen ratio, which has been a theme around Desmos HQ for the past few months. For so many activities—this one included—carving out time to explore what they’ve done on each screen is crucial. There just isn’t enough time to do a 20-screen activity and discuss it. By cutting the screen count in half (from 18 to 9), I’m hopeful that there’s sufficient room for those important discussions to unfold.
  5. Different ending. I pulled the “why do you think it charged that way” question forward to the new Screen 8, which makes room for a new extension on Screen 9. Note two differences: (1) the phone is different, and (2) the direction of the question is different. Instead of “given the charge, what is the time,” it’s reversed: “given the time, what is the charge?”

(Pssst. Did you see that video reveal?)

Lingering Concerns

Is v2 better than v1? In my opinion, absolutely. Is v2 perfect? Not even close.

I think this new version better addresses Principle #8 (“Create objects that promote conversations…”). Fewer screens. More room for conversation.

But I don’t think I’ve addressed the more difficult Principle #5: “Give students opportunities to be right and wrong in different, interesting ways.”

There’s still just one way to move through this activity. It still feels too scripted. Maybe it does live best outside of Activity Builder. Or maybe not. I’ll continue thinking and tinkering. Hopefully most of my steps are forward.


What do you think of the upgrade? Which of the featured comments resonated with you? What could be done to better address Principle #5?

Let me know in the comments, or drop me a line on Twitter.


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