First Lesson of the Year: Prime Factorization

How can you tell your students’ textbook was written by someone who hasn’t taught in a long time, if ever?  Because the first lesson of the textbook is long division!  Ugh!  Welcome back, kids!

No thanks.

Our first chapter (we use the Go Math series) is about Whole Number and Decimals.  It’s basically a review of the 6th grade Common Core standards that overlap with 5th grade topics, with just a few new things added in.

But rather than torture the students and depress everybody with long division right off the bat, I decided to skip to the second lesson, which is prime factorization.

Prime Factorization is very easy to teach, and it’s a good way to determine which of your students know their basic mutliplication and division facts.

I only teach it with the traditional factor tree method.  I kImage result for factor treenow that other methods exist, and our textbook even suggest the “upside down division” method, sometimes called the “ladder method”.  But I really like the visual impact that the factor trees have.  Clearly the composite numbers are being “split” or “broken down” into their prime factors.  It’s representative of division, which is the whole point!

I wind up spending two days on this topic, not because it’s difficult, but because all the procedural aspects of Math class take a long time to explain.  We set up our binders, review our calculator policy, distribute textbooks, and we try to get to know each other.

Along with saving them from long division in lesson #1, I assign a Prime Factorization – Math Monsters Color-by-Number activity, on Day 2.  Prime factorization color by number

It features a wide variety of questions about prime & composite numbers and the steps of prime factorization, and it also questions students about common errors.

prime factorization color by number image.pngPlus, it has another benefit: Students have fun coloring, and they loosen up a bit, realizing that maybe, just maybe, this Math teacher isn’t so bad.  Maybe, we’ll actually have fun in Math this year!

There’s a whole bundle of these Math color-by-number activities in my TpT shop, but as a thank-you for checking out my blog, you can download a free copy right here.  Enjoy!


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