11/06/2011

Sieve of Eratosthenes

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!
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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 and 100.

Enjoy it!
ALICIA
Published by Alicia en 7:49 PM
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19 comments:

  1. destinyNovember 17, 2011 at 10:49 AM

    25 prime numbers

    ReplyDelete
  2. adrian y antonioNovember 17, 2011 at 10:50 AM

    there was 26 prime numbers

    ReplyDelete
  3. Laura and AlmaNovember 17, 2011 at 10:52 AM

    There are 26 prime numbers

    ReplyDelete
  4. Marta y AnaNovember 17, 2011 at 10:53 AM

    Very Good Aliccia!!!

    ReplyDelete
  5. antonioNovember 17, 2011 at 10:53 AM

    Destin son 26
    cuentalos bien

    ReplyDelete
  6. kelvin y ValentinNovember 17, 2011 at 10:56 AM

    1.26 prime numbers

    ReplyDelete
  7. Marta and AndreaNovember 17, 2011 at 10:58 AM

    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. 2
    4. 13-31, 17-71, 37-73, 79-97.

    ReplyDelete
  8. kelvin y ValentinNovember 17, 2011 at 10:59 AM

    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.

    ReplyDelete
  9. Laura and AlmaNovember 17, 2011 at 11:01 AM

    1.26 prime numbers
    2.1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97
    3.2
    4.13 and 31, 17 and 71, 37 and 73

    ReplyDelete
  10. Kelvin y ValentinNovember 17, 2011 at 11:03 AM

    3.2
    4.17 n

    ReplyDelete
  11. María AND MarinaNovember 17, 2011 at 11:04 AM

    1)There are 26 primer 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) number 2

    4)15-51

    ReplyDelete
  12. adrian y antonioNovember 17, 2011 at 11:04 AM

    ej 1:
    26 prime numbers
    ej 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
    ej 3:
    number 2
    ej 4:
    17-71 37-73 97-79

    ReplyDelete
  13. JOHN AND VALENTINANovember 17, 2011 at 11:04 AM

    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.
    3.2.
    4.17-71,37-73,79-97.

    ReplyDelete
  14. destinyNovember 17, 2011 at 11:05 AM

    1.26 prime numbers.1.2.3.13.11.5.7.17.23.19.29.31.41.61.71.43.53.73.83.37.47.67.59.79.89.97.3.2.4.13.31.17.71.37.73.79.97.

    ReplyDelete
  15. Lionel and JoelNovember 17, 2011 at 11:06 AM

    JOEL AND LIONEL .

    The exercise 1 have got 25 prime numbers. 2 1 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 79 83 89 AND 97. 3 97 . 4 73-37 79-97.

    ReplyDelete
  16. destinyNovember 17, 2011 at 11:07 AM

    antonio como que 26 chico

    ReplyDelete
  17. Marta y AnaNovember 17, 2011 at 11:07 AM

    1. 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. 2.

    4. 13-31, 17-71, 37-73 and 79-97.

    ReplyDelete
  18. jose alberto and cristianNovember 17, 2011 at 11:09 AM

    exercice number 1ª: there 26 prime numbers

    exercice number 2ª: the prime numbers are:
    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.

    exercice number 3ª: is the number 1

    exercice number 4ª: 35 and 53, 17 and 71,13 and 31, 37 adn 73, 79 and 97.

    ReplyDelete
  19. AnonymousNovember 17, 2011 at 7:06 PM

    e vuelto a por ti y no me pararas




    muere

    ReplyDelete

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