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Prime Numbers Eratosthenes’ (ehr-uh-TAHS-thuh-neez) Sieve. Eratosthenes was a Greek mathematician, astronomer, geographer, and librarian at Alexandria, Egypt in 200 B.C. He invented a method for finding prime numbers that is still used today. This method is called Eratosthenes’ Sieve.
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Prime NumbersEratosthenes’(ehr-uh-TAHS-thuh-neez) Sieve • Eratosthenes was a Greek mathematician, astronomer, geographer, and librarian at • Alexandria, Egypt in 200 B.C. • He invented a method for finding prime numbers that is still used today. • This method is called Eratosthenes’ Sieve. 276 BC - 194 BC
Eratosthenes’ Sieve • A sieve has holes in it and is used to filter out the juice. • Eratosthenes’s sieve filters out numbers to find the prime numbers.
Definition • Factor – a number that is multiplied by another to give a product. 7 x 8 = 56 Factors
Definition • Prime Number – a number that has exactly two factors. 7 7 is prime because the only numbers that will divide into it evenly are 1 and 7.
Let’s use a number grid from 1 to 100 to see how prime numbers were discovered.
Remove the number 1. It is special number because 1 is its only factor.
