After all of the interesting conversation around Christopher’s (@trianglemancsd) Shapes Book and a conversation with Faith (@Foizym), I thought it would be fun to take this thought about “Which One Doesn’t Belong” into my students’ decimal work. With these decimals, I wanted to draw out reasonings about closeness to benchmarks, equivalents, and properties of numbers in relation to decimals. It did all of that and more! I wrote the following four decimals on the board and had students talk about which one they thought didn’t belong:

In brainstorming these decimals beforehand, I knew that 0.49 would be the most obvious because it is the only one that went into the hundredths, so I go that out of the way as the sample response and asked them to see if they could find another reason for 0.49 or any of the other three decimals. They brought out some pretty great stuff and definitely gave me insight into how they think about multiplication of decimals! It was also so nice to hear, as I walked around during their talk, the freedom students felt expressing their ideas when they knew there was no right or wrong answer!

Kassia (@kassiaowedekind) suggested we start a Google Doc, so I posted this first one and scripted from my students’ journals the responses: Which Doesn’t Belong Google Doc

Feel free to try some with your students…fractions, decimals, whatever and post away on it!

-Kristin

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Cindy FridayThanks for posting the sample responses. They were quite interesting.

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CathyI will try this with some of my junior high students tomorrow. I am excited to see how they answer. Can I add them to the Google doc that Kassia started?

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Cathy Campbell (@ccampbel14)I will try this with some of my junior high students tomorrow. I am excited to see how they answer. Can I add them to the Google doc that Kassia started?

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mathmindsblogPost authorAwesome! Yes, please add away!

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CleargraceMind blown!!

I have to think about this, too. I think it will make a great discussion for my 11th graders!

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lyndalReblogged this on Kauri and commented:

We need to get our students talking more.

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Marian DingleI tried this with my 3 classes of fifth graders. In all 3 classes, a student commented that 0.49 didn’t belong because it was odd. This led to 3 different rich discussions on the definitions of odd and even, a topic that most had assumed was long gone since second grade. They debated each other, rethought their arguments, tested conjectures…it was awesome! Thank you for sharing this problem.

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mathmindsblogPost authorThat is awesome Marian!! Thank you so much for sharing how it went, I love to hear those stories!! It is so crazy to me that I have never thought to revisit even/odd until this year! So much learning around it!

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