At the beginning of the week, we started to look at how to multiply decimals. Easy enough. I have always taught the algorithm, the kids follow the rules, they get it, we move on.
But with the new CCSS, the students are asked to understand conceptually what is going on using models. So, I thought I would break out the old place value manipulatives, show them the breakdown, give the models, and the kids would rise to the occasion and grasp the idea conceptually.
I was wrong.
I mean, they know what they are doing when it comes to the algorithm, but actually understanding the use of the models was a bit challenging. Especially when it came to regrouping to create wholes.
So it was back to the drawing board for me. Upon reflection, I realized that it wasn't the idea of the model that was the problem, it was how I was showing them. Using the place value pieces just wasn't working.
here is a free one I found online for you) and we DREW the model instead of actually using the manipulatives. This worked WONDERS for the kids. They could see what 0.5 x 4 actually meant but didn't get confused when it came time to regroup.
They were really able to see the wholes and how all of the decimal pieces fit together.
The next day, after the model lesson clicked, I thought it would be good to talk about WHY we are actually using multiple strategies. I mean, the algorithm works, so why not just stick with it. After a brief think-pair-share, we created this brainstorm anchor chart together (I am getting good at making them *with* the kids!)
Then, we discussed multiplying decimals specifically, since that is what we were studying. They told me three different ways we learned to solve the same problem, and then listed reasons why we might use that strategy over another.
Finally, as a sort of wrap up, I gave each student one simple multiplying decimal problem and asked them to solve it in three different ways. They then needed to explain why that way would work for them.
All in all, what started out as a flop of a lesson turned into a good learning experience for us all. Does that ever happen to you? What lesson did you teach that just didn't take off in the right direction for you? How did you fix it?