Variety of methods and answers. One thing that went well in facilitating the number talk today was, in two classes, students early on clearly made mistakes in their calculation. No one called out and said “no, you’re wrong”, and we calmly moved on to the next person. Each student figured out their mistake, and one volunteered to correct it on his own.
One student realized that the border is 12×12 – 10×10. I was excited about that, but one student isn’t a big win. Gotta figure out how to facilitate that discussion so I can get a bunch of other students in on that conversation.