Split 25 with grade 8s

Today I had the opportunity to lead a grade 8 class through the split 25 question “thinking classroom style”.

we got into random groups of 3 using my team shake app, and then working at the boards I gave this prompt. Split 25 up into pieces. Example: 20+5 or 1+1+1+1+1+…+1 and then multiply all the pieces together, so we’d have 20×5=100 in the first case and 1x1x1x1x1x…x1=1 in the second case. We want to split up 25 in a way that maximizes the product of the pieces.

Groups knew the rules of 1 marker per group, and the person with the marker writes the thoughts of the other members.

We had some interesting approaches. Some groups used big pieces, some used small pieces, some used equal sized decimal pieces, and one group wanted to start off thinking about negative pieces (something I didn’t expect at all).

With a bit of experimenting and some calculators, we got right into the task.

Some groups got really big values for the product, but still are searching for the biggest.
I consolidated the task by talking about thinking creatively and responding well to challenges, and also we talked about how to write their repeated multiplications with exponents, so it could be a more streamlined process of they continue calculating at home.

I’m proud of them for diving in and giving it a good try. I’ll have to bring another good challenge to them next week.