This morning we studied what Primes and Composites are. Here you have the definitions.
It was created by Eratosthenes (275-194 B.C., Greece), an ancient Greek mathematician. Just as a sieve is a strainer for draining spaghetti, Eratosthenes's sieve drains out composite numbers and leaves prime numbers behind. The numbers from 1 to 100 are listed in a table. We will use The Sieve of Eratosthenes to find all primes up to the number 100 by following the directions below.
- Cross out 1 since it is not prime.
- Circle 2 because it is the smallest prime number. Cross out every multiple of 2.
- Circle the next open number, 3. Now cross out every multiple of 3.
- Circle the next open number, 5. Now cross out every multiple of 5.
- Circle the next open number, 7. Now cross out every multiple of 7.
- Continue this process until all numbers in the table have been circled or crossed out.
Questions (to be answered as a comment):
1. How many prime numbers are there from 1 to 100?
2. List all prime numbers from 1 to 100.
3. Which number is the only even prime number?
4. An emirp (prime spelled backwards) is a prime that gives you a different prime when its digits are reversed. For example, 13 and 31 are emirps. List all emirps between 1