#5 Math Minute: Sieve of Eratosthenes


Image from Wikimedia Commons

A sieve is a kitchen utensil that is used to strain solids from liquids or for separating coarser from finer particles.  The Sieve of Eratosthenes is similar because it’s used to separate out all the prime numbers from a given set of numbers.

How can you spend your Math Minutes this week?

  • What is a prime number anyway?  What is the smallest prime number?  Is 1 prime?  Why or Why not?  Are all odd numbers prime?  How many prime numbers are there between 1 and 100?  Watch this video and listen to a catchy rap about Prime Numbers and then post a comment answering one or more of the questions posted.
  • Watch this video about the Sieve of Eratosthenes.  You can even print out this 100 chart and follow along with the video.
  • Read this article and find out about Eratosthenes.  Consider the following questions as you read:
    • What were 2 of Eratosthenes’ nicknames and what did they mean?
    • What is Eratosthenes known for besides the Sieve named after him?
    • What kind of man was Eratosthenes?
"Eratosthenes." Famous Scientists. famousscientists.org. 21 Jun. 2014. Web. 9/18/2015 

11 thoughts on “#5 Math Minute: Sieve of Eratosthenes

  1. The two nicknames are Beta and Pentathlete. Beta means something that could be used as an insult or a compliment. Pentathlete means to be very good at 5 sports, but probably will not be a champion in the individual sports.

  2. One is NOT a prime number, a prime number has only two factors, itself and one. It can’t be multiplied by any other numbers.

  3. The steps are big, but I did them and now I understand how to do them. Before I met with Mrs. Spady, I had never heard of these steps before. I knew about strainers/seives before, but I never knew they had a name in math. Thank you Mrs. Spady!

    1. Actually, all even numbers but the number 2 are composite. Prime numbers only have 2 factors, 1 and itself. Composite numbers have more than 2 factors. All even numbers have 1 and itself as factors, as well as 2 because they are even.

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