Sieve of Eratosthenes: An ancient way of finding prime numbers.Eratosthenes was a mathematician and librarian in ancient Alexandria. He invented an algorithm, called the sieve of Eratosthenes, to collect prime numbers. This fun chart helps students see not only the prime and composite numbers, but has the multiples of 2, 3, 5, 6, 7, and 10 colored a special way on the chart. This is a great reference for students to use throughout the year. Making factor trees, prime factorizations, reducing