Where’s Poly? An Exploration in Geo-Dotting

What’s geo-dotting?  I have no clue but that’s what I’m calling this lesson.

We started by asking, “What do you notice?”

Where's Poly (Geo-Dotting) copy.003.jpeg

Our favorites:

  • Looks like Pac-man
  • I see dots and they make a “Y”
  • Looks like someone went crazy with a hole punch

We needed to wrangle in student thinking a bit so we gave them some information…

Where's Poly (Geo-Dotting) copy.004.jpeg

Where's Poly (Geo-Dotting) copy.005.jpeg

Unanimous vote. “I see a square and a triangle.”

We asked students to explain their reasoning and one said:

I know there are 7 corners, I mean “vertexeses”, and 4 of them make up a square which leaves 3. I can’t make a shape with less than 3 dots because then it’s not a shape. So the only shape I can make with 3 dots is a triangle.

We have a winner…

Where's Poly (Geo-Dotting) copy.006.jpeg

Now that students had the hang of it, we went here next…

Where's Poly (Geo-Dotting) copy.008.jpeg

What do you notice?

We let them play, talk, and share for a couple minutes and triangles seemed to be the shape of choice.  Then we revealed the mystery polygons.


By now we felt students were ready to tackle the opening slide again.

Where's Poly (Geo-Dotting) copy.003.jpeg

On our second time around there was no Pac-man or letters, only shapes.  But this time instead of just talking about the dots, students were encouraged to put their thinking on paper.

Screen Shot 2016-12-05 at 2.11.56 PM.png

Students used only the top three boxes for about 5 minutes. This allowed them to flush out each other’s misconceptions.

This helped students construct their own understanding.

After about 5 minutes we slow-released the following criteria, giving them one new nugget every 3 minutes:

  • Total of 5 shapes
  • No dots left over and each dot can only serve as 1 vertex for 1 shape
  • Shapes can overlap
  • Only 2 triangles
  • One square and one rectangle

Students compared work to ensure the criteria was met.  “Looks like you have 2 rectangles in the bottom corner. Try again.”

As we wrapped things up, students came to the board and shared their solutions.

Screen Shot 2016-12-05 at 1.16.34 PM.png

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My takeaways:

  • Talking about the shapes and their properties before moving to paper really allowed for students to engage in SMP#3 once we made the leap.
  • The slow release of information allowed students the opportunity to build problem-solving stamina.

If you want to give the lesson a try here’s the slides in a pdf file and student work mat. Please report back and let us know how it goes.  I’m wondering what takeaways you can share.

About gfletchy

K-8 math consumer trying to listen and learn each day. Stay thirsty my friends!
This entry was posted in Geometry, Making Math Accessible, Who Knows?. Bookmark the permalink.

14 Responses to Where’s Poly? An Exploration in Geo-Dotting

  1. Michelle Bittick says:

    What grade levels are you suggesting use this lesson?

    • Stephanie Rousseau says:

      Michelle – I was wondering the same but thinking Gr 2/3 based on the Geometry content standards in those grades. With that said, I think even older students could get a lot out of it as well, reinforcing properties of polygons.

      • gfletchy says:

        It actually could fit in kindergarten because the shapes students are drawing. The 5 shapes here are all aligned to their standards. But with that being said you could definitely push this way up into high school if you wanted. If you do I’d love to hear how it goes. Please report back.

  2. senorstadel says:

    Awesome idea. I feel like you’ve been geo-dotting for years.

  3. Paula says:

    I just did this lesson in a grade 5 class – lots of great conversation around the attributes of various polygons. The gradual release of clues was key for the last slide. Some of those early finishers thought they had it… until I introduced the next clue. Made all of them THINK.

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  6. Molly says:

    We did this lesson in a grade 2 class yesterday and it was so much fun! The kids were so engaged and excited about each new clue! I am going to co-teach it again tomorrow in another grade 2 class and look forward to more ah-has and excitement! I plan to try it with other grades too! Thanks for sharing!

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  8. mybeautifuldestruction says:

    This is awesome!!!

  9. Jennifer D Lagrange says:

    Hi! I tried this with my kindergarten class last week and another teacher in my grade tried it with his class this morning. So interesting! I intended to only do the first three slides of dot images, but got stuck on the second with the dots which could be the corners of a square and a triangle. Both of our classes had students who thought there was a rectangle in the middle. :-O Basically, it was clear to us that our students know that rectangles have four corners and four sides. But we never talked about four right angles! So this activity was great for formative assessment and now we will go back and address that. We plan to look at a variety of 2D shapes which have four sides & corners but may not be rectangles. Keep up the good work Mr. Fletchy!

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