I’m switching my tactic — there weren’t enough kids talking about the math — even if we hear from 5 or 6 students explaining their strategies, kids attention starts to wane, and it’s a small fraction of the class. Instead, I took all answers, and borrowed language from Sadie Estrella around making sure every answer that was in a students’ head is on the board. Then students share their strategies. It’s small, but making more students feel that their participating is meaningful is what I need with number talks right now.
Anyway, my favorite part of this number talk was the impressive variety of ways students moved numbers around to make it easier to calculate — or in some cases, didn’t move numbers around, and made their calculations harder. The commutative property of multiplication is a huge part of well-developed number sense, and a surprising number of my students don’t take advantage of it — for instance this mistake that Michael Pershan posted a while back.