Greedy Triangle

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The student will be able to identify basic two-dimensional shapes in the world around them.

Big Idea

When we look closely, we can see that our world is made of shapes, repeated over and over again.


10 minutes

The Greedy Triangle is a classic read in Elementary math because it covers content in a fun and silly way.  When putting together lessons for the content areas I am always on the look out for the books available in our school library.  Starting my math lesson with a book engages my students; fifth graders still enjoy being read to.  It also is important to connect content areas, such as math, with language arts to help students make these thinking connections.

Most times I am pleased and surprised at the book choices I can find in the school library.  Often, I am able to draw inspiration from the books, using them as a spring board into creating a great lesson. When designing this lesson I used the story of The Greedy Triangle to deliver the content in a fun context.

In the story, the author creates a triangle as the main character, who finds his shape to be boring. After locating a shapeshifter, the triangle is able to add a side to his shape and observe his new shape in the objects around him.  For example, when the triangle turns into a quadrilateral he sees himself (as a shape) in doors and windows.  But the triangle is never happy with his shape, and he continues to add sides and changes as a shape.  By the end, the triangle realizes being a triangle wasn’t as boring as he thought.  As you can see this is a very cute story and my fifth graders really enjoyed it. 

I began this lesson by reading the story to the students.  I stopped at each page and had the students turn and talk to a neighbor about their predictions and thoughts.  I have included a few examples of pages from the book.


30 minutes

Now it is time for the student to become the illustrators! 

I ask the students to think of one of the shapes in the story and create their own illustration for a page in this book.  Before beginning to draw, I review a few pages so students can visualize how the triangle saw himself in the everyday world. 

I didn’t give many guidelines for this assignment because it is very dependent on individual creativity.  Sometimes less is more when assigning work to the students.  I will say, I am pleasantly pleased with the products of the majority of my students' work.  


5 minutes

The students were really excited about their creations and wanted to share.  I think it is really important in elementary school to do a lot of student led sharing.  This helps build their confidence and prepares them for the many times in the future they will have to do some sort of public speaking.

Students individually present, using the document camera to share their illustration.  The expectation is that in sharing they explicitly point to and explain their shapes, using the appropriate math vocabulary.

My expectations for sharing are to speak in a voice everyone can hear, make eye contact with the class, and use our Accountable Talk norms when answering questions.