Building Perimeter

5 May

Area and perimeter have always been a doozy to teach, not because the concepts are so difficult but because students tend to mix them up.  When we get into problems like “keep the perimeter the same, but create the smallest and largest areas you can,” their heads really spin.

Enter the popsicle sticks.  It turns out that popsicle sticks are the perfect perimeter building material.  They could take the number of sticks they needed to represent a given perimeter (like 12) and create different rectangles.  Then they would count the squares inside and find the area.  You know an activity is a success when your strongest mathematicians want to build, and your struggling students are successful.

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Afterwards, students transferred their work to graph paper and wrote about which perimeter made the largest area.

 

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We had a discussion afterwards about what kinds of shapes made the largest areas (fat ones–the closer to a square, the better)and what kinds of shapes created the smallest area (long and skinny.)  Some students also came up with mathematical ways to create create shapes with a certain perimeter besides guess and check.  They discovered that for a perimeter of 14, for example, you need to create a shape with two sides that add up to 7, which then doubles for the opposite 2 sides.  Not all students were ready for that logic, but it spread through about half of the class.  Area and perimeter really lend themselves to building, we’ll have to do more in the future!

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