## Thursday 26 February 2015

### MFM2P - Day 17 (Similar Triangles)

I am currently in Toronto about to spend 2 days working with Apple. So this post and the next one are "what should happen", not what happened in class.

Today's warm up is this Would You Rather:

I did this one with my 2P class last semester. This may seem like a simple calculation exercise, but it was challenging for some. Many calculated how much they would make in a day, then in a week, then in a month, then in a year and they did not get the same answer as someone who went from one week to one year. There was some interesting debate about how many hours per day is "normal" - is it 8 hours or 7.5 hours? If you work on a per hour basis, does that include vacation time or sick leave? (Some of these questions are addressed on the WYR site, but I wanted my students to think about them.)

The plan for today is to learn how to find missing side lengths in similar triangles and practice that skill. I am trying to encourage them to highlight corresponding sides in matching colours and label corresponding angles with the same symbols. I find that they understand how to find the length of a missing side best by first calculating the scale factor. I suggest doing large triangle over small triangle so that the scale factor represents how many times bigger the large triangle is compared to the small triangle. (They are always welcome to use other mathematically correct methods.)

Here are a couple more examples to work through with them:

They will practice a little more (page 3 of this handout) and then they will work on this handout which includes a few shadow and mirror questions.