11/08/2010

Erathostenes Sieve

The Sieve of Eratosthenes is an ancient method for finding all primes numbers up to a specified number.

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.

Directions:

  1. Cross out 1 since it is not prime.
  2. Circle 2 because it is the smallest prime number. Cross out every multiple of 2.
  3. Circle the next open number, 3. Now cross out every multiple of 3.
  4. Circle the next open number, 5. Now cross out every multiple of 5.
  5. Circle the next open number, 7. Now cross out every multiple of 7.
  6. Continue this process until all numbers in the table have been circled or crossed out.
You have just circled all the prime numbers from 1 to 100!


Questions:

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 and 100.

Enjoy it!
ALICIA


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14 comments:

  1. RAQUEL AND ÁNGELA
    1.26
    2.1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97.
    3.Is 2
    4. 13-31,17-71,31-13,37-73,71-17,73-17,79-97.

    ReplyDelete
  2. ANSWERS:
    1: 26.
    2: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.
    3: 2
    4: 13-31, 17-71, 37-73, 79-97.

    MIGUEL GUERRA, JESÚS PÉREZ Y AARÓN RODRÍGUEZ

    ReplyDelete
  3. 1. There are twenty six prime numbers from 1 to 100.

    2.The list is : 1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,57,61,67,71,73,79,83,89 and 97.

    3.The number two.

    4.The list is: 31,71,32,13,73,37,97,79.

    Andrea Cobo y Andrea Magro

    ReplyDelete
  4. 1.twenty six are the prime numbers.
    2. 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,
    59,61,67,71,73,79,83,89,97.
    3. the number two.
    4.13 and 31,17 and 71,19 and 91,37 and 73,79 and 97.
    Javier Diaz and Javier Bravo.

    ReplyDelete
  5. 1.26 prime numbers
    2.1,2,5,7,11,13,17,19,23,29,31,37,41,43,47,53, 59,61,67,71,73,79,83,89,97
    3. the only prime number is 1
    4.13 and 31,17 and 71,37 and 73,79 and 97.


    tony e ivan

    ReplyDelete
  6. 1.There are 26 prime numbers from 1 to 100
    2.1,2,3,5,7,11,13,17,19,31,37,41,43,47,53,59,61,67,71,73,79,83,89 and 93.
    3.The only prime number is 2.
    4.Are: 73/37, 71/17,97/79.



    Gabriela Estefania Tapu - Irene Del Cerro Ortiz

    ReplyDelete
  7. Names:Beatriz,Gloria and Natalia.
    1. there are 26 numbers.
    2.1,2,3,5,7,11,13,17,19,23,29,31,41,43,47,53,59
    61,67,71,73,79,83,89 and 97.
    3. the number 2.
    4. the numbers are: 13-31, 17-71, 37-73 and 79-97.

    ReplyDelete
  8. we did bad the exercise 2 is 2



    tonyy e ivann

    ReplyDelete
  9. Question 1:26
    Question 2:1,11,31,41,61,71,2,3,13,23,43,53,73,83,5,7,17,37,47,67,97,19,29,59,79,89
    Question 3:2
    Question four:11/11,13/31,17/71,37/73,79/97
    Anthony and roberto 1ºe

    ReplyDelete
  10. 1)26 numbers
    2)1 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
    3)the number two
    4)13-31 11-11 79-97 17-71 37-73

    JaViEr MeSa y Carlos gil

    ReplyDelete
  11. Answers:
    1.There are 26 prime numbers.
    2.1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89 and 97.
    3.Is the number 2.
    4.13=31,17=71,37=73 and 79=97


    Sara Adraos y Marta Fernández

    ReplyDelete
  12. We did bad the exercise 2, the correct answer is 2.

    Ivan and Antonio

    ReplyDelete
  13. 1. Twenty six prime numbers from 1 to 100.

    2.1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,57,61,67,71,73,79,83,89 and 97.

    3.Number two.

    4.13-31 79-97 37-73 17-71

    Lydia y Paloma

    ReplyDelete