## Which One Doesn’t Belong?

31 Mar

You’ve seen “which one is different” before.

(I first remember seeing this particular question from John Bament at a T3 session in 2014, although he might have gotten it from somewhere else. He sent it to the participants as a Quick Poll and showed us our quite varied results.)

You’ve seen “Odd One Out” before.

These two images come from the Mathematics Assessment Project formative assessment lesson on Comparing Investments.

I observed this lesson in a classroom a few weeks ago. It didn’t bother students that more than one answer can be correct, and they naturally explained why they chose what they did without the teacher even having to prompt them with “How did you get that?” or “Why?”

My coworker and I introduced Christopher Danielson’s Which One Doesn’t Belong to our beginning K-2 teachers recently. They began to think immediately about how they could do something similar with language as well as math. (And they were thrilled to learn something in PD that they could immediately take back to their classrooms.)

When I recently learned about Mary’s Which One Doesn’t Belong site, I decided to spend some time on it during our recent Math PLC meeting.

We started with a page from Christopher’s shape book. Our assistant principal (former history teacher) was thrilled to be able to immediately participate in our discussion. (How many of our students feel the same when we offer them low-floor, high-ceiling tasks?)

We did a number WODB (one teacher fist-pumped another assistant principal when they figured out that 9 didn’t belong since the sum of its digits isn’t 7). Thanks, Pam!

Then we moved to Rachel Fruin’s geometry Which One Doesn’t Belong. Our history teacher-turned assistant principal was still able to participate. She didn’t have the same vocabulary that the rest of the math teachers in our department had when stating why one doesn’t belong, but she learned some math vocabulary and we learned to see the images through different eyes during our shared experience.

We ended our PLC with Hunter Patton’s Graphs & Equations 7.

I recently heard that one measure of the success of professional development is whether the teacher’s practice changes as a result of what was learned. (Another part to this would of course be how long the teacher’s practice changes … one lesson? A few lessons? Or permanent change in lessons?) So I was thrilled to notice that the teacher with whom I share a room gave her precalculus students a WODB to try at the end of their opener later that day.

They were studying rational functions. Which one doesn’t belong?

Before I knew it, students were in different corners of the room based on their initial responses.

They shared thoughts with each other before sharing with the whole class.

I tried the geometry WODB with my geometry students yesterday. I asked them to send me their response so that I could decide whether moving to one of the four corners of the room would be worthwhile. I asked bottom left to gather, bottom right to gather, and then top left & top right to gather. Why doesn’t your choice belong?

Now work on your mathematical flexibility. Instead of being satisfied with one way to answer, find multiple responses.

Find a reason that each one doesn’t belong, and let me know when you do by selecting that choice on the new Quick Poll (now multiple response).

Now sorted by individual responses so I can see which students need support:

I’ve offered problem solving points for students who create their own WODB, and I look forward to seeing the results. Thank you, Mary, for creating a place for us to share and learn together … for creating a site that our teachers were able to immediately incorporate into their own learning and their students’ learning.

### 5 responses to “Which One Doesn’t Belong?”

1. March 31, 2015 at 8:14 pm

• March 31, 2015 at 8:17 pm

Great! See http://wodb.ca for lots of great ideas, and I’ll try to catch you tomorrow to talk!

2. April 1, 2015 at 10:56 am

This has got to be the best new idea ever in the teaching of math.

3. April 1, 2015 at 5:18 pm

I am going to use one of these during our revisit day tomorrow. I will have 9-10 parents in the room (Alg2) and I know if I choose wisely, they can participate too!

4. April 15, 2015 at 7:22 pm

27,29,31 which one doesn’t belong and why?