Tuesday, June 01, 2010

A Surprising Finals Question (Apparently)

I gave the following 2 sets of questions on my algebra 1 final (click on it to enlarge):

For 13 & 14, they were given a line and were to draw a parallel line going through (4,1) then give me the equation in point-slope form. For these 2 questions, people generally did fine.

For 15 & 16, I had the same original line drawn, and they were supposed to draw the perpendicular line through (4,1) and then give the equation in point-slope form. This is the set of problems they had problems with.

I thought I was giving them a gentle teacher nudge by having them draw the picture before they wrote the equation. The original slope is -2/3. Holy Moly. So many students thought NOTHING of the fact that the line they drew was NOT perpendicular looking. They INSISTED the slope of the perpendicular line had to be 2/3, and by Golly, that's the line they drew. 90 degrees? eh!

Note to self, when I teach algebra 1 again, I have to do more of this type of problem before we get to finals. I never did do the drawing thing in conjunction with just the "what's the slope/equation/etc of the perpendicular line to ..." type of question. Apparently, I should have.

On a positive note, I'll be teaching them geometry next year, so guess what we'll be "reviewing".


  1. Great approach and great problems. Sorry they've quit thinking.

  2. Hey, Kate at f(t) had an excellent activity for just this type of problem. I think it was called 20 questions or something like that. I plan on using it next year for precisely the reasons you are talking about. If your pre-ap kids had trouble with this, you can just imagine the trouble my ninth graders are having with this topic.