First Try at 3 Act Math

I’ve been wanting to teach math through 3 Act lessons for quite some time but haven’t seen the path or prioritized figuring it out. This weekend, as we prepared to work on area and perimeter I spent some time thinking about how to make it happen.’

So yesterday I told my 3rd graders that I wanted to start a vegetable garden in back yard. I explained that I’m not good at gardening so I need help. I also told them that lots of critters (deer, raccoons, turtles, rabbits) are around back there so I need a fence and I want to mulch my garden to make sure the vegetables have a great growing space. Then I showed them this picture.


I asked them how I could figure out how much fence and mulch I need to buy. They had some great conversations which included a lot of guessing. One girl finally said we needed to measure around the garden to figure out how much fence. So I put up this picture.


I didn’t tell them what to do with that, but gave it to them. Then we continued with the conversation about mulch. They knew mulch comes in a bag (which I didn’t expect them to know) so I showed them this picture.


We noticed this bag will cover 12 square feet. Huh. What’s a square foot? Again, an interesting discussion. I showed a ruler we’ve been using and we talked about it being a foot, so what is a square foot? Another girl told me to get three more rulers and make a square with them. So we did and figured out a square foot. Then we could see a way to measure for mulch so I showed this picture.


Again, I didn’t tell them what to do with it, just gave it to them. Off they went to figure out how much fence and mulch I need. Lots of interesting work happened. After about 15 minutes we came back together and a few students shared what they had done to find the perimeter or the area. They headed off again and after another 10 minutes or so most of my students had figured out both answers.

Today, while I’m home sick, the new intern I’m working with will be taking them through helping her figure out how much carpet and wallpaper border she’ll need in a new (rectangular) apartment. Can’t wait to see how they do!

If you’re interested, here are some documents.


area-and-perimeter-garden-plot (I would give everyone the first page here and make the other pages available if they need them.)

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