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Prime and Composite
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First I put the tiles in 1 row, and count how many columns.
Let’s Review Find the factors of 9. First I put the tiles in 1 row, and count how many columns. 1 x 9 = 9
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Then I try to make 2 equal rows…
Let’s Review Find the factors of 9. Then I try to make 2 equal rows… 1 x 9 = 9
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So I will try to make 3 equal rows.
Let’s Review 3 x 3 = 9 Find the factors of 9. I can’t make 2 equal rows!!! So I will try to make 3 equal rows. 1 x 9 = 9
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1 x 9 = 9 3 x 3 = 9 Factors of 9: 1,3,9 Let’s Review
Find the factors of 9. Factors of 9: 1,3,9 Write the factors in order from least to greatest. If a number has more than 2 factors it is called COMPOSITE!
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First I put the tiles in 1 row, and count how many columns.
Find the factors of 11 First I put the tiles in 1 row, and count how many columns. 1 x 11 = 9
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1 x 11 = 9 Find the factors of 11 I can’t make 2 equal rows!!!
Then I try to make 2 equal rows… I can’t make 2 equal rows!!! So I will try to make 3 equal rows. 1 x 11 = 9
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1 x 11 = 9 Find the factors of 11 First I put the tiles in 1 row, and count how many columns. I can’t make 2 equal rows!!! So I will try to make 3 equal rows. I can’t make 3 equal rows!!! So I will try to make 4 equal rows. Then I try to make 2 equal rows…
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1 x 11 = 9 Find the factors of 11 First I put the tiles in 1 row, and count how many columns. I can’t make 2 equal rows!!! So I will try to make 3 equal rows. I can’t make 3 equal rows!!! So I will try to make 4 equal rows. Then I try to make 2 equal rows… I can’t make 4 equal rows!!! So I will try to make 5 equal rows.
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1 x 11 = 9 Find the factors of 11 First I put the tiles in 1 row, and count how many columns. I can’t make 2 equal rows!!! So I will try to make 3 equal rows. I can’t make 5 equal rows!!! So I will try to make 6 equal rows. Then I try to make 2 equal rows… I can’t make 3 equal rows!!! So I will try to make 4 equal rows. I can’t make 4 equal rows!!! So I will try to make 5 equal rows.
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1 x 11 = 9 Find the factors of 11 If a number ONLY has 2 factors it is called PRIME! I can’t make 6 equal rows!!! And I have less than 2 complete columns… so there are no more combinations! First I put the tiles in 1 row, and count how many columns. I can’t make 5 equal rows!!! So I will try to make 6 equal rows. I can’t make 2 equal rows!!! So I will try to make 3 equal rows. Then I try to make 2 equal rows… I can’t make 3 equal rows!!! So I will try to make 4 equal rows. I can’t make 4 equal rows!!! So I will try to make 5 equal rows.
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How do I know if a number is prime or composite?
A number is composite if it has more than 2 factors, therefore I know it is composite if I find at least 2 factor pairs. Prime means that a number only has 1 and itself as a factor.
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Use divisibility rules to help determine if a number is prime or composite
7 63 88 Prime Composite The only factors of 7 are 1 and 7… so it is PRIME. It is a even number.. So 2 is a factor, therefore it is composite If I add the digits I get a multiple of 3, so 3 is a factor… it is composite.
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Use patterns to help determine if a number is prime or composite
53 34 Prime Composite If a 3 is on the ones place, and it is not a multiple of 3, then it is PRIME Except for 2 and 5. All other primes have a 1,3,7, or 9 in the ones place. What other patterns do you see?
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Solve Try it Out!
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Which numbers are prime?
Ⓐ 7 Ⓑ 24 Ⓒ 29 Ⓓ 41 Ⓔ 68 Ⓕ 77 a,c,d
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Write a composite number that is greater than 16 and less than 20.
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