## Thursday, January 4, 2018

### Perimeter & Area of Similar Figures

We're in the heart of our dilations and similarity unit in Geometry and my students have started being surprised when we aren't using the computers that day. So thankful for our recently expanded access to more devices for our kiddos.

I love starting my unit with this amazing Working with Dilations activity. It builds the concept of similarity from similarity transformations, which I love. It also helps students visualize how the center of dilation and the k value influence the image. It made the compass and straight-edge construction for a dilation a "duh" kind of moment....OF COURSE that's how you do it!

 Students doodling on pattern block mats to show their thinking.

I designed the next activity so students could discover the relationship between scale factor and ratios of perimeter and area. Students use a combo of interactive shapes and pattern block mats to discover the pattern! I took the idea from a Big Ideas Math activity and adapted it:

Perimeter and Area of Similar Shapes Desmos Activity

Overall, it went well. My students this year are struggling a bit more with abstraction that they have in the past, but they enjoyed the activity and once one person in the group saw that pattern they were excited to see it for themselves.

Feel free to steal, adapt, or offer suggestions for improvement!