Wednesday, February 02, 2011

What's enough for a parallelogram to appear?

Whew! We've graduated PAST triangles to quadrilaterals in geometry, and now we're cruising. The first day I showed some Internet clips/pics about scissor lifts and pantographs and wood routers that are made like pantographs and such to show parallelograms in "the real world". Then we explored by measuring and conjecturing about the 5 (6) properties of parallelograms. The 2nd day I started with this sheet:

I had a brief discussion with them about what could you "get away with" and magically GET a parallelogram for free if you were creating an object that needed to be a parallelogram. It may be more costly or time consuming to force 2 pairs of parallel opposite sides instead of some other properties that might save you some time or money. Then they discussed with whatever tools they wanted, and then we converged as a class. I made sure to either have them draw a picture at the end as a counter example to the shape being FORCED to being a parallelogram, or we did a "flow proof" to show some were forced.

Today was a crazy day. It started out as 17 degrees F in the morning and up to the 20's during the day, and our city/state had rolling brown outs to be able to handle the load of everyone trying to stay warm I guess. Anyway, at school we were in a ratio of 45:15 off:on electricity practically all day. Sheesh! Thank goodness we have TONS of windows. But BOOOO on the lack of microwaves and coffee pots for the essentials: lunch and caffeine!


  1. Anonymous3:23 PM

    This is great timing - I'm doing parallelograms tomorrow, and I will definitely use your worksheet! Thanks for sharing! :)

  2. We are doing parallelograms as well. I have a great special parallelograms investigation sheet. Not sure if I know how to post it. Let me know if you're interested.

  3. Glad you can use the sheet .... and, Karen, sure! It's always fun to have extra resources (instead of teaching in a vacuum). If you figure out how to post it, let me know ....