I will remind students to show work as they solve and be prepared to discuss their solutions. As noted in the comments section of the task, there will be some discussion and perhaps confusion over finding the perimeter of the green and red shapes. I think it will be simplest just to have students find the total distance of the border around the shaded regions including the holes.
When students struggle, I will ask questions like the opener: What fraction of a circle is present? What fraction of the square is shaded or not shaded?
We will share out our findings. I will call on groups to present their solutions. I will try to make time to discuss at least two different solution methods per problem. Here is an opportunity for students to critique the reasoning of others or construct a viable argument for their solutions (MP3).