Monday, October 20, 2014

Multiplying Decimals with Models....Oh How I Love Sheet Protectors!

Ever had a Monday that felt like a Friday?  Well, that was today for me!  Oh, the Monday blues! But, no matter what, the teaching must go on!

I was pretty concerned with teaching my 5th graders how to multiply decimals using models.  This summer, I went to about 4 trainings on how to do it......and then I slept! :)  Despite the students acting like it was a Friday, they did AWESOME on our whole class lesson on how to multiply decimals with models.

Each student had a sheet of paper I made in PowerPoint that was inside of a sheet protector, two different colored Expo markers, and a kleenex.  And away we went!

      We went over at least a dozen examples of how to multiply with models, and the students did great.  I think it was using the Expo markers that did the trick!  Anything different is exciting, right?!?!

We really spent time discussing how the number of boxes "shaded" with both colors was not a whole number but a number out of the 100 boxes in the grid.

We went step-by-step through the process each time, eventually with the students telling me which step I needed to do next.

First, we shaded in the tenths represented with the first number vertically.  We used diagonals to make it easier to see the eventual overlap.  If we had colored in the squares, the Expo markers wouldn't really show where the two overlapped, making determining the solution difficult.

Then we shaded in the tenths associated with the second number horizontally.

We then determined how many on each hundreds grid had the "double cross" with the X's made from both of the two different colors.

Students then added those two numbers together to get the final solution.

It was so nice to see the lightbulbs going off as we went through examples.  Some of my students who really struggle with math were volunteering to tell me the next step or give the answer.  Moments like that are all a teacher ever wants!

We then put examples in our Math ISN.  I made the hundreds grids the size I wanted them and cut out enough for each student to have six for their ISN.  Do you think I'm crazy for cutting them all out? Ha!  There's just never enough time, it seems, and I didn't want to spend time having the kids cutting them out when I could over the weekend.

We will still be practicing this tomorrow, and then we move on to using the standard algorithm to multiply decimals.  It was really amazing hearing some students discuss how they would work this out with the standard algorithm just from today's activity.  Exciting things happening in Ms. Green's classroom!  Students making the connections is what makes all those trainings and weekends spent making activities so worth it!

Have a great week!!!


  1. I love this! Do you have the pdf of the sheet you put inside the sheet protectors?

  2. Will be using this tomorrow. We ventured into the wonderful world of multiplying decimals by powers of 10 today and this is our next step! Thanks :-)