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Which One Doesn’t Belong?

Summer Math Camp = Five Days +  Educators + a Focus on Learning

We spent quite a bit of time considering the underpinnings of the frame for the five-day program. After considerable deliberation, we determined the structures we would use to engage the campers in thinking about teaching and learning would be exactly what we want classrooms to be built upon:

  • Building Community
  • Promoting Conversation
  • Encouraging Exploration

We then moved to the next step in our planning: THE HOW?

How do we accomplish this? How do we make it a transparent component of the five days? How do we start camp? The how was following by and connected to the what. What opening task would we choose and how will it support our underlying structures?

The Question: What do you choose to be the opening task?

The Answer: Which One Doesn’t Belong?

We started with this image from Christopher Danielson’s book, Which One Doesn’t Belong? and asked everyone to take a moment to consider which shape doesn’t belong and why.

Screen Shot 2015-07-17 at 8.40.48 AM

The educators then thought about these two statements:

  1. Provide more than one reason that the shape you chose might not belong
  2. Offer a reason why each of the shapes might not belong

We asked that they ensure that each person in their group had enough time to ponder, notice, and formulate ideas prior to engaging in a group conversation.

The Result: LOTS of conversation

We then showed the next image, from the website Which One Doesn’t Belong.Screen Shot 2015-07-17 at 9.19.36 AM

After the table conversations were concluded and a brief whole group discussion was had, chart paper and markers were distributed, and directions to create a WODB that your students could discuss in the opening week of school were posted. The groups set to work creating their posters.

The energy and the conversations the groups generated were amazing. We heard consideration about number size, entry points for all kids, WODB as a formative assessment tool for the Standards for Mathematical Practice, specifically practice #3, and all kinds of important stuff.

After the charts were finished, they were posted around the room.


Each camper grabbed some post-it notes, selected a chart that was interesting, and off they went on a gallery walk. We used the following protocol for the gallery walk.

  • Take a moment and individually think about the options displayed on each chart
  • Decide which one doesn’t belong
  • When all members of your group are ready, share ideas and explanations
  • Select one of the ideas and the explanation and record it on the wrong side of a post-it note, and attach it to the chart

A side note: If the ideas are written on the wrong side of the post-it note, groups are not influenced by the ideas already shared. If a group wants to check out what others have written, they can always check after posting their idea. The team that developed the chart will have a larger set of original ideas, not just variations on a theme.


At the end of the gallery walk, the team retrieved their chart, discussed the information on the post-it notes, and made revisions, as needed.

The Opening Task debrief encompassed the following topics:

  • general thoughts
  • feedback from the gallery walk
  • instructional moves that were used
  • the critical idea of providing an entry point for a task
  • inclusion of all kiddos into the conversation

What I learned:

  1. It is really hard to resist the question “which one doesn’t belong?” even at 8:15 am on a lovely summer morning.
  2. Gallery walks need to be purposefully structured. When organized as such, they become a strong instructional tool that promote mathematical conversations.
  3. When the teacher participates, students emulate the academic modeling.
  4. The closing structure of the opening task needed to be stronger, more focused on the learning and the learner. It needed something similar to the question written by Nicora Placa her blog post on Bridging the Gap.

Doing mathematics: Write a about the activity from the perspective of a learner. Think about the learning processes. What helped you as a learner? What helped you sort out the mathematics?

Over the course of the next two weeks, I’ll be using a similar version of the opening task with a few groups. I am interested in how the use of a different closing reflection might impact the learning and the learners.


  1. Talking Math With Your Kids–a blog hosted by Christopher Danielson
  2. Which One Doesn’t Belong–a blog hosted by Mary Bourassa
  3. Bridging The Gap–a blog hosted by Nicora Placa
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