An Instructional Routine for “Which One Doesn’t Belong?”

We are currently studying geometry. The standards for geometry list one important understanding to develop before 4th grade, “Reason with shapes and their attributes.” If you click through the link you can read more about the specifics, but the activity that gets students reasoning about shapes and their attributes the most, in my opinion, is Which One Doesn’t Belong? This activity allows students to share their thinking about shapes and their properties without the fear of being wrong. Why? Because every answer is correct as long as you can justify your reasoning! You can read more about how I implement “Which One Doesn’t Belong?” in my class and you can use it for more than just geometry.

But this post is about how I used this activity as a basis for an instructional routine. Continue reading


The amazing science podcast, Radiolab, recently did a show titled “Worth.”  Andrew Stadel, over at Divisble by 3, blogged about some math problems this podcast made him think of.  The podcast didn’t necessarily make me think about math problems, instead it made me consider reasoning about value and quantity.  More specifically, is everything quantifiable?

Google defines “quantify” in this way:

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Which makes me wonder can everything be expressed or measured in a quantity?  Can everything be quantified?

Radiolab gives three instances in which things are given a dollar amount that would not normally be thought of in this way.  It gives worth to things that are normally thought of as “priceless.”

Does everything have a price?

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