Wednesday, April 19, 2017

Don't Let Composite Figures Eat Your Lunch

Don't let composite shapes eat your lunch! I was skimming through instagram a few weeks ago and everyone was teaching composite shapes...and complaining about how hard they are.'s because they are totally hard!!!! 

So many steps, lots of specifics, and lots of room for error makes it so difficult for us to help students to  navigate how to solve for area and perimeter. 

Here's how to not let composite shapes {{and}} finding their area and perimeter eat your lunch!

Divide up the shapes
I have seen this look of fear when students have to divide up composite shapes to find the area. It's like they don't know where to begin. Sides, area, numbers, units...forget about it! Just practice dividing up shapes sans measurements. 

Also it's important to talk about strategy of dividing up the shapes. While there really isn't a wrong way to divide up a shape there are defineitly ways to divide up shapes to reduce room for error. 

You know that the few divisions there are the fewer smaller areas to add up. But sometimes it's best to divide the shape up a little more. It's dependent on each composite shape but it's so important to talk about why we are dividing the shape up and how to do it with the least possible mistakes to find the area. 

You allll know that students get lost in perimeter in these composite shapes and what's the best way to hone in on that? ABC123 THE SIDES. 

We assign each side a letter and write down the measurement in a quick made table. That way students know if there are any missing measurements. Thennnn they count the side to double check they've all been assigned. 

Some students prefer vertical tables and other's really up to them and how they ever feel organized. 

I think this is my favorite part because it's so hands on and lends itself to so much discovery and light bulb moments. You know when you bring into "toys and treats" that your students interest and engagement is like EVERYTHING. SO BUILD. Make. Create.

I love bringing out the magformers, starbursts, saltines, cheese it's, post it's and any square shapes manipulatives and snacks. Target has some great small post-its that are square shaped. They are all perfect for finding area and perimeter. I am especially fond of startbursts because students can color code how they partition up the composite shape to find the area like in the picture below    

Just a heads up to get at least three bags for enough of all of the isn't enough to build with or to snack on after ;)


Like any math standard it's important that your students take ownership. I have students create their own...whether grids or tiles and find the area and perimeter of composite shapes. It's worth all of the work!!! I love this activity above because it is simple, it shows each students understanding.

What are your tips for teaching composite shapes? I'd love to hear them! Because....ummm...they are hard!

You can find all of these fun shapes in my store and the task cards here. ((This is my composite shape will be posted this week!))

Be sure to follow me by clicking the green star so you get my updates! I am posting some more composite shape fun stuff in the near future...that I am so excited about!

Over and Out!


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