Mentor Text Sunday: Prime Numbers Anyone?

Today I wanted to share with you a fun math text that I like to use in my classroom with my Smarties.
Amanda and Stacia, those Collaboration Cuties have  mentor text sharing day on Sundays, and I love to read about all of the different books that people use in their classrooms.

Have you read The Librarian Who Measured the Earth by Kathryn Lasky?  This is a great book about an ancient Greek philosopher and mathematician named Eratosthenes.  He did so many wonderful things including measuring the circumference of the Earth using ratios more than 2,000 years before Columbus sailed to America!
I actually use this book when I am reviewing Prime Numbers.  It fits perfectly in my curriculum because we also study Ancient Greece, so I read the book and discuss the connection to social studies as well.  Eratosthenes is responsible for recognizing that all numbers can be factored down to a set of primes.  His philosophy is called the Sieve of Eratosthenes, and when you are teaching your students to make prime factorization trees, you are actually re-creating parts of this "sieve."  After reading the book, I have my students "discover" all of the prime numbers between 1- 100 using a hundreds board.  This is a great way to review divisibility rules.

Because my smarties have to be able to simplify fractions, they must know about common multiples, and factors,  I also use this book as an intro/review to least common multiples, and greatest common factor.

I use an Interactive Notebook for mathematics, and my students love including the hundreds board with divisibility rules in it as a reference tool.  I do have a unit in my TpT store if you need a little bit to help you out with this topic.  The unit includes specifics about the sieve lesson and book, a foldie and directions for showing your students the ladder method of prime factorization, LCM, GCF and even simplifying fractions.  You can go {HERE} if you are interested in checking it out.

You can of course use this book to teach ratio as well, since as I mentioned Eratosthenes measured the circumference of the Earth which mathematically he calculated with only a 1.6% error... AMAZING if you think that this was in about 240 BC!
Stop by and visit the Collaboration Cuties and read more about the math mentor texts that teacher's are using in their classrooms!


  1. This looks like a great book. I haven't seen it before but I think my kiddos would enjoy it.

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  2. This looks like a fun book! I need a book for prime and composite! I will definitely have to check it out! It sounds like you can use it for many different things!

    Thanks for linking up Michele!
    Collaboration Cuties


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