Multiplication Fluency

We’re working on multiplication strategies these days, and we got out the base 10 blocks to model some multiplication. We did 15×6 to start with.

Some students made 6 groups of 15, and then counted. They knew they had 6 groups of 10, and 6 groups of 5, so the total was 90. Others used doubling and halving with this question. They doubled the 15 to make 30, and they halved the 6 to make 3, then they multiplied 30×3 and got 90. They then used 9 rods of 10 to build the 90, or used 100 and a negative 10 rod to get back to 90. It was neat to see the different ways students approached the problem.

We next looked at 26×15 to see if there were different approaches.

One group built a rectangle thar had dimensions of 26 and 15. We can see (top right) that this gives us a nice area model to work with. We can section the rectangle by friendly numbers and then calculate the small areas and add them up. Another group kept using the doubling and halving. They doubled the 15 to get 30, and halved the 26 to get 13 then did 13×30. Some did 13x3x10 to make it easier. Either way you get 390. One group made the 390 in a 3D shape and another made it in a flat rectangle, starting off with 400 and removing one by using a negative 10 rod.

I’m really glad my students are getting braver and are excited to share their strategies. Here’s one student’s area model. We needed a small correction, but it was a great way to show our work.

Next we used our multiplication strategies to work through a number string, doing one question at a time sequenced in an order to help us get to more complex problems by using work done in prior questions.

We’ll keep working on these strategies. It’s fun to see the learning happen!