I’m working on a professional development session for tomorrow (don’t judge me…), and I’ll be introducing mental math computation strategies for multiplication to my 3rd-5th grade teachers using the book Number Talks. One great feature of this book is the DVD that’s included. It contains video clips from classrooms and, as the saying goes, a picture is worth a thousand words. It’s just very cool to see and hear kiddos talking about their strategies for mental computation.
One of the goals of number talks is to increase students’ understanding of properties. We probably all remember memorizing the commutative, associative, and distributive properties in school, but did they really mean anything to you? Many teachers are familiar with using the partial products method for introducing multi-digit multiplication. Partial products is really based on the distributive property, because you are breaking the numbers into parts and then using the distributive property to combine them. Traditionally, it looks like this (notice the distributive property notation beneath it):
But partial products is also a strategy for single-digit multiplication. Consider 7 x 8. A common strategy that kiddos use to solve 7 x 8 is to think of 7 x 7 and add one more group of 7. Hmmm, wouldn’t that be the distributive property?