Stop! It's a hexagon!
by John Pearson
Quick – can you identify the shape of a speed limit sign? How about a yield sign? What about a stop sign? You're correct if you said rectangle, triangle, and not a hexagon.
Geometry is always a fun topic to teach. At the third grade level, geometry really amounts to identifying shapes. The kids have at least heard of most of the flat shapes – pentagon, trapezoid, hexagon, octagon – but the 3-dimensional shapes are brand new to them.
For some reason, they immediately understand that soda cans and soup cans are cylinders. However, anything else that has a round component throws them for a loop. They'll frequently identify the wall clock, a bus tire, and a doughnut as spheres. The cylinder/sphere controversy, though, is nothing compared to the pyramid/prism issue.
For anyone unfamiliar with the jargon, a pyramid is a 3-dimensional shape whose faces are triangles that meet at an apex. The base, or bottom face, can be any shape, and that shape lends its name to the pyramid. Thus, you have triangular pyramids, square pyramids, rectangular pyramids, etc. The Pyramids in Egypt are square pyramids. A triangular prism, on the other hand, looks like a pup tent. It has only two triangles, on opposite ends, separated by rectangular faces.
I suppose the confusion arises because there are triangles involved with both shapes. Kind of like the confusion in telling Tommy Boy and Black Sheep apart because both movies involve Chris Farley.
I've tried all sorts of things to help the kids remember the differences between prism and pyramid, but there are always those who just don't get it.
Back to the 2-dimensional shapes now. Of all the shape names, the kids love hexagon the best. How do I know this? Because that's their first response to just about ANY shape beyond circle, square, triangle. When they see a stop sign, their initial thought is, "Oooh! Hexagon!" When I ask them to count the sides, and they see eight, they know it's an octagon. Unfortunately, on a test, I'm not able to grant them a second guess.
See, the kids are pretty good when it comes to remembering how many sides each shape has. They know that an octa-gon had eight sides because an octa-pus has eight arms. And they know that a hexagon has six sides because hexagon has an “X” in it, and six is the number that has an “X” in it.Of course, this little trick DOES cause confusion in the kids who say, "hectagon” and “oxagon.”
Getting the kids to slow down and count the sides instead of just picking their favorite answer is the truly difficult part. If only there was a way to ensure that the kids remembered their traffic signs before choosing a name. Then perhaps they would Yield their thoughts, Stop their initial impulse, and more closely resemble Slow Children at Play.
John Pearson is a third-grade math and science teacher in Dallas, Texas. He has degrees in mechanical engineering from Duke University and Texas A&M, so most consider his math abilities adequate enough to teach nine-year olds. He is also the author of Learn Me Good (Lulu, 2006), a funny, fictionalized account of his first year in education. Read more at learnmegood2.blogspot.com
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