Sunday, August 31, 2014

Making Sense Out of Multiplication...

It seems as though the longer I teach, the more it seems that students just really have difficulty using the multiplication algorithm. When I started to see this more often a few years back, I began to implement the "matrix" or "grilled cheese" method of multiplication. Kids still had trouble with this. It seemed as though this was just a skill that the kids just have to learn. Recently, however, I began to think about how this skill could be learned differently. My students seemed to be pros at multiplying various numbers by a one digit number. I am sure someone else has thought of this before, so I am in no way taking credit for multiplying this way... but when I implemented this method into my Math Enrichment class I saw the light bulbs turn on and it was so exciting that I just had to write this blog. So if you have beat the traditional multiplication algorithm into the ground and are still having students struggle with multiplying, you may want to give this a try. (Bonus: this also shows a real use for the Distributive Property!)

I started my lesson off with some really simple problems involving mental math.

This was to help the students to start thinking about instances where it is easy to use mental math. 

Next, I introduced the idea of breaking up a multiplication problem on the following manner.

By breaking up the first part of the product in this way, the student will ultimately have two very easy multiplication problems to evaluate...

What is nice about this method is that once the second number in the multiplication problem is distributed, the student has two problems involving a number multiplied by a single digit number. This eliminates the need to remember the steps that are involved in multiplying by a two digit number and allows students to utilize some mental math, which makes the whole process much quicker.

Finally, the student just has to add both of the products of the two problems that they completed and they have the product of the original problem. My students (even though they tend to struggle with remembering how to multiply) do very well with this method. The ones that were pretty good with the traditional algorithm, find that this way helps them to multiply more quickly, so they also like using it. I hope you will try this with your students! It has done wonders for mine. 

I will be posting more about this in days to come. Thanks for reading and Happy Teaching!

1 comment:

  1. Hi,

    I happened to chance upon your blog and found it very interesting!

    We have recently launched a science app that uses augmented reality to enhance classroom teaching. The app has 3D models for kindergarten to grade 12. I thought you might want to check it out and may be review it on your blog, if possible.

    It is a paid app(with a few models free) but in case you are interested in trying it out I will be happy to provide you with a free copy.

    The link to the app is:



    You can also search for the app on the app store as 'Augmenter'.

    Do let me know if you would be interested. I am really Looking forward to your response.

    happy teaching!