Monday, August 31, 2009

Let's Drop This Tennessee-Is-a-Parallelogram Nonsense

Yesterday in the car Meyer and I were having a conversation about quadrilaterals. Meyer wanted me to explain parallelograms. Searching for an example, I nearly made the mistake of saying, "Tennessee is shaped like a parallelogram." I'm glad I caught myself.

The Tennessee-as-parallelogram meme is a common educational device, both in the Volunteer State and elsewhere in the country. Thanks to minutes of research on Google, I found it in public school curriculum from Mississippi and Ohio. In the Biloxi, MS document, Tennessee's supposed parallelogram shape is the subject of a story problem:

The state of Tennessee resembles a parallelogram. Its height is approximately 100 miles, and its base is approximately 380 miles. Find the approximate area of Tennessee.

Here's the problem: Regardless of what they say here, here, here, or here, Tennessee does not at all resemble a parallelogram.

As you can see above, if one approximates Tennessee's borders using a quadrilateral, the north and south borders are nearly parallel. The east and west borders are not. Not even close. Thus Tennessee resembles a trapezoid—with one pair of sides that are parallel and one pair of sides that are not. If you're looking for a parallelogram–two sets of parallel sides—use Colorado or Wyoming (which also happen to be rectangles).


Blogger Matt Wittlief said...


But it's much harder to calculate the area of a trapezoid!

8:40 PM  

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