Exploring Sets with Knobbed Cylinders

I had our little set of Knobbed Cylinders near my desk and it caught my eye when I was looking for something to give to Luke so he’d let me get some work done.

I don’t recommend buying the mini Montessori knock-off cylinders, by the way. We have not gotten much use out of them. I hear the full-size ones (with ten pieces per row instead of five) are better but they’re also so expensive that I’m not sure they’re worth it for home use.

Luke has long outgrown our mini cylinder set. Nathan’s starting to be a good age but I can’t let him play with it unsupervised because it is full of choking hazards. I had it stashed on my desk and when Luke was pestering me about something, I passed it to him to give him something to do.

Then I remembered the post about sets I had read the other day on the Fairy Math Mother. (Isn’t that a wonderful name for a blog?) Kelly writes about sorting objects into sets based on different attributes.

I’ve also been seeing “which one does not belong” prompts on Twitter. These are designed so that one can make an argument for each object being different from all the others, so the fun is seeing how different people think. Is it the top right because it has no peel or the bottom left because it’s only half of a Cutie? (And who cuts a Cutie anyway?)

So first with Luke, I made little sets of three cylinders and asked him what was the same and what was different about them. Some were all the same height but with different widths and some had the same width but different heights.

He was using “bigger, medium-er and littler” to describe both how tall and how wide. This was a good opportunity for me to introduce vocabulary like height and width.

Then I made a few sets where there was an odd one out and we talked about how that one was different and did not belong in the set.

At the end we sorted all the pieces into sets based on how tall they were. I pointed out one set that was different from all the others, because it had pieces that were the same height and width.

I asked Luke if he noticed any other sets that were different from all the others. He pointed out the set that had a lot of pieces in it. The set with eight tall pieces was different because all the other sets only had three pieces.

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