Divisibility Rules, Prime Numbers, GCF, and LCM

Can you believe it is already October?  I am amazed that in just another week our first quarter of school will be over!  It seems like yesterday was Meet the Teacher.

We spent a ton of time this week reviewing divisibility rules and prime numbers.  My students have REALLY been struggling with this, and I knew I had to take a week from my normal sixth grade curriculum and do a quick review.  I started by having them put a foldable in their notebooks that gives the divisibilty for 2,3,6,9, 5 and 10.

After my students got a little more comfortable with divisibility, we took on Prime Numbers.
First in the lesson I showed my students a video of Eratosthenes.  He is teh Greek philosopher who is credited with finding that all numbers can be factored into primes.  The video focuses on Eratosthenes as a whole person.  He is also credited for finding a very accurate measure of the circumference of the Earth using a sundail.  Here is the video:

We use a hundreds board and divisibility rules to find all of the prime numbers from 2-100 and color code them on the board.  

We add the hundreds chart to our notebooks and complete a sorting activity for prime and composite numbers.  

We had to relearn GCF in order to be successful using this concept with combining like terms and the distributive property.  I teach LCM and GCF using the prime ladder method as well, so we spent the rest of our week practicing this new concept.  I think that combining like terms will be so much easier next week!  When I teach LCM and GCF I use a foldable as well.  You can read the original blog post I wrote about this lesson {HERE}  If you are interested in any of the foldables you can go {HERE}.  The lesson plan I use to teach finding the prime numbers on a hundreds chart is also included in the packet.  I also have a BUNDLE which includes the lesson plans for each concept, interactive notebook foldables and practice problems.  Check it out {HERE}

I would love to hear how you teach these concepts!  Please feel free to share below!

1 comment

  1. When I do Prime and Composite, I use Red and Green colors. Red for Prime, means stop I can't break it down to more factors. Composites are Green, means go I can still break it down for more factors.


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