Prime Numbers
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Prime Numbers

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    Prime Numbers Prime Numbers Presentation Transcript

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