Classifying Polygons

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One of my classes is in the middle of a unit on geometry and measurement.  They’ve identified shapes before, such as rectangles, squares, triangles and hexagons.  Earlier in the year they found the area and volume of shapes involving rectangles, squares and triangles.  The current unit investigates how polygons (specifically triangles and quadrilaterals) are similar and the study of shapes progress as students create hierarchies.

    Understand that attributes belonging to a category of two-dimensional figures also belong to all subcategories of that category. For example, all rectangles have four right angles and squares are rectangles, so all squares have four right angles.


In order to dig deeper into the above standards the students starts the classification process.  This was fairly new for most of the students.  I explained what classification meant and gave a few examples related to the characteristics of triangles and quadrilaterals.  Students were given a sheet of quadrilaterals to cut out and classify.  The next question I was asked was related to how each shape should be categorized.  The class reviewed different vocabulary words associated with polygons and then I left the students create their own categories.

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This student decided to split up the shapes into three categories.  3-sides, 4-sides and 4+.

After discussing equal side lengths and parallel sides two of my students created the classifications related to those terms.

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Almost every student had a different way to organize their shapes.  Students went to different tables and observed how their peers classified the shapes and then the class discussed similarities.  Next week students will classify the shapes with a hierarchy chart.  I’m looking forward to seeing what they create.

Polygon Hierarchy

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My fourth grade class has been exploring geometry and polygons.  They’ve been comparing polygons and looking closely at how to classify them.  Students are familiar with these shapes and can classify them by their looks. Students were confident early in the week as they were able to label polygons based on side length, angles, and sides.  Things started to change when the word hierarchy was introduced.  The word is new to most of my students so the class first reviewed the term.

Students were then given a paper full of shapes.  They cut out the shapes and used their desk to classify them.  Students classified the shapes according to their attributes.  Some students sorted the polygons by angle size, while others used symmetry or side length.

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Students were finished in about ten minutes.  The class took a gallery walk and reviewed all the other ideas.  Students discussed which polygons met or didn’t meet the category title.  Students then went back to their seats and reviewed the term hierarchy again.

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The class took the cards and taped/glued them to make their own hierarchy.  Students are starting to see the characteristics of polygons in a different light.  This is good news as later on in the year students will use polygon characteristics to find area measurements.  They’ll also be transforming the polygons on a grid in about a month.

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I’m looking forward to the polygon discussion tomorrow.

Side note:  This is my 300th post.  I had no idea that I’d be writing so much over the years, but it’s been an amazing journey.