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?”

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…

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…

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

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.

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.

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

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

**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.

So glad to have found this website/blog and love this idea to get students engaged and have fun with what they’re learning. Could be a great formative assessment exercise too. Awesome! I’ll be back!

Awesome! I was wondering how you use the second lot of card where the dots are hidden?

Hi Naini…can you please elaborate? I’m not sure what cards you are referring to.

Hi Graham

I’m sorry. My computer was probably not loading the images and some dots appeared to be covered by a blank square. I thought it may be another strategy you were using. They are all appearing now!

As a geometry teacher I am always looking to find rich and good activities for my classes. This activity “Where’s Poly? An Exploration in Geo-Dotting” is a great example of introductions to polygons. The students were so into the lesson from the beginning to end of the class. It was interesting to hear students’ opinions and see their engagement. I liked all the purposeful questions that the teacher asked the students during their lesson. The teacher also guided the students to the final solutions by slow releasing information. That allowed the students to improve their problem-solving abilities.The students explained the mistakes they made to each other, resulting in finding the right answers. I liked the idea of having a competition-like lesson and have a winner. By the end of the lesson, the students were explaining their final solutions on the board. The students enjoyed the class by exploring new concepts. Great activity! Do you have a similar activity for High School Geometry?

This reminds me of Zukei Puzzles. https://buildingmathematicians.wordpress.com/2018/03/08/zukei-puzzles/

My students love these.

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!

This is awesome!!!

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!

Hello! This post was recommended for The Best of the Math Teacher Blogs 2016: a collection of people’s favorite blog posts of the year. We would like to publish an edited volume of the posts at the end of the year and use the money raised toward a scholarship for TMC. Please let us know by responding via http://goo.gl/forms/LLURZ4GOsQ whether or not you grant us permission to include your post. Thank you, Tina and Lani.

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.

Right on Paula. I guess both of our missions were accomplished. Thanks for sharing.

Dude!

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

Since I was in the womb brotherman! I’m a geo-dotter for life!

What grade levels are you suggesting use this lesson?

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.

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.

Thank you for the feedback!!!