# + 5.3a Prime & Composite Kim Norman GES 2014 + Eratosthene of Cyrene Born: 276 BC in Cyrene, North Africa (now Shahat, Libia) Died: 194 BC in Alexandria,

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+ 5.3a Prime & Composite Kim Norman GES 2014

+ Eratosthene of Cyrene Born: 276 BC in Cyrene, North Africa (now Shahat, Libia) Died: 194 BC in Alexandria, Egypt

+ Sieve of Eratosthenes

+ Since 1 is not prime, color it purple

+ Sieve of Eratosthenes Circle the 1 st prime number, 2 with your pencil Color every multiple of 2 on your chart yellow

+ Sieve of Eratosthenes Circle the next prime number, 3 with your pencil Color the multiple of 3 on your chart red (some multiples of 3, such as 6 and 12, may already be colored yellow. Ignore these and look for the uncolored multiples 16

+ Sieve of Eratosthenes Circle the next prime number, 5. Color any uncolored multiples of 5 blue. 6

+ Sieve of Eratosthenes Circle the next prime number, 7. Color any uncolored multiples of 7 green. 3

+ Sieve of Eratosthenes Count the uncolored squares on your chart Can you find 25 of them? If you can, then you have sifted out all of the prime numbers under 100

+ Primes & Composites BrainPop Numbers & Operations Prime Numbers

+ What are Prime Numbers? ?

+ Definition A whole number with exactly two factors, 1 and itself

+ What are Prime Numbers? Characteristics Whole number Only has 2 factors 1 and itself

+ What are Prime Numbers? Examples 2, 3, 5, 7, 11… Example: 2 is a prime number 2 x 1 (only 2 factors) Example: 13 is a prime number 13 x 1 (only 2 factors)

+ What are Prime Numbers? Non-Examples 0, 1, 4, 6, 8, 9…

+ Is 1 a Prime Numbers? How many factors does the number 1 have? Answer = 1 A Prime Number has to have 2 factors So, the number 1 cannot be a Prime Number

+ What are Composite Numbers? ?

+ Definition A whole number that has more than two factors

+ What are Composite Numbers? Characteristics Whole number Has more than 2 factors

+ What are Composite Numbers? Examples 4, 6, 8, 9, 10… Example: 4 is a composite number 1 x 4 2 x 2 (4 has more than 2 factors, it has 3 factors) Example: 12 is a composite number 1 x 12 2 x 6 3 x 4 (12 has more than 2 factors, it has 6 factors)

+ What are Composite Numbers? Non-Examples 0, 1, 2, 3, 5, 7…

+ Is 1 a Composite Numbers? How many factors does the number 1 have? Answer = 1 A Composite Number has to have more than 2 factors So, the number 1 cannot be a Composite Number

+ So 1 is… Neither Prime Nor Composite

+ Prime, Composite, or Neither…  6  9  7  1  3  5  2  4  10  8

+ Prime, Composite, or Neither…  21  60  25  100  32  29  1  81  72  37

+ Finding Prime & Composite Lets use Connecting Color Tiles

+ Rectangles Chart NumberFactorsNumber of Rectangles Prime or Composite 1 2 3 4 5 6 7 8

+ 1 = Neither Prime (only 2 factors) Nor Composite (more than 2 factors) 1 only has one factor

+ 2 = Prime 1 x 2(2 factors)

+ 3 = Prime 1 x 3(2 factors)

+ 4 = Composite (3 factors) 1 x 4 2 x 2

+ 5 = Prime 1 x 5(2 factors)

+ 6 = Composite (4 factors) 1 x 6 2 x 3

+ 7 = Prime 1 x 7(2 factors)

+ 8 = Composite (4 factors) 1 x 8 2 x 4

+ Can You Tell the Difference Between Prime & Composite Numbers? http://www.321know.com/fra63ax2.htm

+ XPMath Primes vs. Composites Monkey Drive Fruit Splat King Kong's Prime Numbers Prime or Composite?

+ Now it’s time for the… Prime and Composite Quiz Any questions? Are your ready? Great, let’s get on IA iTest and get started… SOL5.3aQuiz

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