Wednesday, April 10, 2013

Geometry: Two Dimensional Areas

The year is winding down, and it's time for 2D area, 3D surface area and 3D volumes. I know my geometry kidlets have been learning areas of triangles since they were in the womb, so I didn't want to spend much "lecture/learning" time on it. I also wanted to do something different for parallelograms. Basically, I wanted them to spend the bulk of the period on practicing challenging area problems.

So, I thought I'd have them draw a large (palm sized) triangle in their notebooks, and then we would eyeball all 3 altitudes by lining up the ruler markings with the base to allow perpendicular segments. We'd measure everything in cm, then use calculators to get area.

We also talked about accuracy and how since we are measuring to the tenths place and THAT'S iffy, then when we calculate, we can only expect accuracy to the integers place.

Once we did this, I asked if anyone was off more than an integer for their 3 calculated areas (the 3 scenarios of bases and heights). Some kids were off a lot.

Well. It seems that I wasn't clear or it wasn't clear and I just assumed they'd know which base matched up with which height. Silly me.

So I went back and color coded my notebook and had them do the same. Here is what it looks like:


  1. I wish there were a pinnable image on this post, so that I could save it to my pinterest board! I love the highlighting. Highlighters are my best friends in teaching geometry.

  2. Hmmmm, didn't think of that. Thanks! Let me try to put it up a 2nd way.