I gave students patty paper, a ruler and an image with 2 similar figures. They were provided with some guiding questions & their task was to conclude the properties necessary for figures to be similar. Next year I’d like to make this more rigorous by providing students with a collection of pairs of polygons that are similar & pairs that are not and leave off the guiding questions. I think it would be a much richer task. I felt like I was dragging them along instead of letting them explore.
After this activity, I projected a series of images of similar figures and students decided if they were similar or not and explained how they knew.