Prime Numbers

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Prime Numbers

  1. 1. Prime NumbersEratosthenes’ Sieve<br />By Monica Yuskaitis<br />
  2. 2. Copyright © 2000 by Monica Yuskaitis<br />Eratosthenes(ehr-uh-TAHS-thuh-neez)<br />Eratosthenes was the librarian at<br /> Alexandria, Egypt in 200 B.C. <br />Note every book was a scroll.<br />
  3. 3. Copyright © 2000 by Monica Yuskaitis<br />Eratosthenes(ehr-uh-TAHS-thuh-neez)<br />Eratosthenes was a Greek mathematician, astronomer, and geographer.<br />He invented a method for finding prime numbers that is still used today.<br />This method is called Eratosthenes’ Sieve.<br />
  4. 4. Copyright © 2000 by Monica Yuskaitis<br />Eratosthenes’ Sieve<br />A sieve has holes in it and is used to filter out the juice.<br />Eratosthenes’s sieve filters out numbers to find the prime numbers.<br />
  5. 5. Copyright © 2000 by Monica Yuskaitis<br />Definition<br />Factor – a number that is multiplied by another to give a product.<br />7 x 8 = 56<br />Factors<br />
  6. 6. Copyright © 2000 by Monica Yuskaitis<br />Definition<br />Factor – a number that divides evenly into another.<br />56 ÷ 8 = 7<br />Factor<br />
  7. 7. Copyright © 2000 by Monica Yuskaitis<br />Definition<br />Prime Number – a number that has only two factors, itself and 1.<br />7<br />7 is prime because the only numbers<br />that will divide into it evenly are 1 and 7.<br />
  8. 8. Copyright © 2000 by Monica Yuskaitis<br />Hundreds Chart<br />On graph paper, make a chart of the numbers from 1 to 100, with 10 numbers in each row.<br />
  9. 9. Copyright © 2000 by Monica Yuskaitis<br />Hundreds Chart<br />
  10. 10. Copyright © 2000 by Monica Yuskaitis<br />1 – Cross out 1; it is not prime.<br />
  11. 11. Copyright © 2000 by Monica Yuskaitis<br />Hint For Next Step<br /> Remember all numbers divisible by 2 are even numbers.<br />
  12. 12. Copyright © 2000 by Monica Yuskaitis<br />2 – Leave 2; cross out multiples of 2<br />
  13. 13. Copyright © 2000 by Monica Yuskaitis<br />Hint For Next Step<br />To find multiples of 3, add the digits of a number; see if you can divide this number evenly by 3; then the number is a multiple of 3. <br />2 6 7<br />Total of digits = 15<br />3 divides evenly into 15<br />267 is a multiple of 3<br />
  14. 14. Copyright © 2000 by Monica Yuskaitis<br />3– Leave 3; cross out multiples of 3<br />
  15. 15. Copyright © 2000 by Monica Yuskaitis<br />Hint For the Next Step<br />To find the multiples of 5 look for numbers that end with the digit 0 and 5.<br />385 is a multiple of 5<br />& 890 is a multiple of 5<br />because the last digit<br />ends with 0 or 5.<br />
  16. 16. Copyright © 2000 by Monica Yuskaitis<br />4– Leave 5; cross out multiples of 5<br />
  17. 17. Copyright © 2000 by Monica Yuskaitis<br />5– Leave 7; cross out multiples of 7<br />
  18. 18. Copyright © 2000 by Monica Yuskaitis<br />6–Leave 11; cross out multiples of 11<br />
  19. 19. Copyright © 2000 by Monica Yuskaitis<br />All the numbers left are prime<br />
  20. 20. Copyright © 2000 by Monica Yuskaitis<br />The Prime Numbers from 1 to 100 are as follows:<br />2,3,5,7,11,13,17,19,<br />23,29,31,37,41,43,47,<br />53,59,61,67,71,73,<br />79,83,89,97<br />
  21. 21. Copyright © 2000 by Monica Yuskaitis<br />Credits<br />Clipart from “Microsoft Clip <br />Gallery” located on the Internet <br />at http://cgl.microsoft.com/<br />clipgallerylive/default.asp <br />

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