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Factors, Divisibility, & Prime / Composite numbers Next Lesson 1d

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Factors & Divisibility Definition: A number is divisible by another number if, when you divide, the remainder is 0. 24 0 24 is divisible by 8. 18 6 24 is not divisible by 9. factor Since 24 is divisible by 8, 8 is called a factor of 24. Here are all the factors of 24. Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24 Next

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2 12 = 24, Factors & Divisibility cont... The number 24 is a multiple of each of its factors. 4 6 = 24,3 8 = 24, Multiples of 2 are: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30,... Multiples of 3 are: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36,... Multiples of 4 are: 4, 8, 12, 16, 20, 24, 28,... Multiples of 6 are: 6, 12, 18, 24, 30, 36, 40,... Multiples of 8 are:8, 16, 24, 32, 40, 48, 56,... Multiples of 12 are:12, 24, 36, 48,... Multiples of 24 are:24, 48, 72,... 1 24 = 24 Next

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Factors & Divisibility cont... Thus, divisible by, factor of, and multiple of are related terms. 4 6 = 24,12 2 = 24,8 3 = 24, 24 is divisible by 8. 8 is a factor of 24. 24 is a multiple of 8. 1 24 = 24 Next

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Example 1 Choose True or False for each sentence. (a)12 is a factor of 60.True or False?TrueFalse (b)25 is a factor of 60.True or False?TrueFalse (c)19 is divisible by 8.True or False?TrueFalse (d)30 is divisible by 15.True or False?TrueFalse (e)12 is a multiple of 12.True or False?TrueFalse (f)36 is a multiple of 9.True or False?TrueFalse Next

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Answer A is True because : 12 5 = 60

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Answer B is False because : 50 10 25 is not a factor of 60.

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Answer C is False because : 16 2 19 is not divisible by 8.

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Answer D is True because : 30 0 30 is divisible by 15.

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Answer E is True because : 12 1 = 12 12 is a multiple of 12.

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Answer F is True because : 9 4 = 36 36 is a multiple of 9.

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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,,13, 14, 15 Example 2 List all the factors of 15. List all the numbers through 15. Divide 15 by each number in the list. Reject each divisor that produces a nonzero remainder. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,,13, 14, 15 Answer: 1, 3, 5, 15

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Your Turn On a piece of paper, list all the factors of 9. Click here to check your answer

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Divide 9 by each number in the list. Reject each divisor that produces a nonzero remainder. 1, 2, 3, 4, 5, 6, 7, 8, 9 List all the numbers through 9. 1, 2, 3, 4, 5, 6, 7, 8, 9 Answer: 1, 3, 9 The Process

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Your Turn On a piece of paper, list all the factors of 22. Click here to check your answer

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Divide 22 by each number in the list. Reject each divisor that produces a nonzero remainder. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 List all the numbers through 22. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 Answer: 1, 2, 11, 22 The Process

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Your Turn On a piece of paper, list all the factors of 5. Click here to check your answer

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1, 2, 3, 4, 5 Divide 5 by each number in the list. Reject each divisor that produces a nonzero remainder. List all the numbers through 5. 1, 2, 3, 4, 5 Answer: 1, 5 The Process This is a prime number which we’ll discuss later in the lesson

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Divisibility Tests are shortcuts for finding factors of whole numbers. Here are six useful divisibility tests: 1.A number is divisible by 2 if the last digit is an even number. 2.A number is divisible by 3 if the sum of its digits is divisible by 3.A number is divisible by 3 if the sum of its digits is divisible by 3. 3.A number is divisible by 4 if the last 2 digits name a multiple of 4.A number is divisible by 4 if the last 2 digits name a multiple of 4. 4.A number is divisible by 5 if the last digit is 0 or 5.A number is divisible by 5 if the last digit is 0 or 5. 5.A number is divisible by 9 if the sum of its digits is divisible by 9.A number is divisible by 9 if the sum of its digits is divisible by 9 6.A number is divisible by 10 if the last digit is 0.A number is divisible by 10 if the last digit is 0. Click the text for Examples

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Examples: 411 4 + 1 + 1 = 6 A number is divisible by 3 if the sum of its digits is divisible by 3. 9,855 9 +8 + 5 + 5 = 27 2 + 7 = 9

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Examples: 1036 36 = 4 9 A number is divisible by 4 if the last 2 digits name a multiple of 4. Since 36 is divisible by 4, 1036 is also!

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Examples: 10, 25, 40, or 75 are all divisible by 5 because the last digit is a 0 or a 5 A number is divisible by 5 if the last digit is 0 or 5.

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Examples: 153 1 + 5 + 3 = 9 9 is divisible by itself. A number is divisible by 9 if the sum of its digits is divisible by 9. 468 4 +6 + 8 = 18 9 2 = 18 Since 18 is divisible by 9 then 468 is also!

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Examples: 10, 20,40, 70, 110, 2190 are all divisible by 10 because the last digit is a 0. A number is divisible by 10 if the last digit is 0.

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Practice Which of these numbers are divisible by four? 11620281114 Yes No Click here to review the shortcuts again

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Click here to review the shortcuts again Practice Which of these numbers are divisible by three? 513982 Yes Yes No

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Divisibility Tests are shortcuts for finding factors of whole numbers. Here are six useful divisibility tests: 1.A number is divisible by 2 if the last digit is an even number. 2.A number is divisible by 3 if the sum of its digits is divisible by 3. 3.A number is divisible by 4 if the last 2 digits name a multiple of 4. 4.A number is divisible by 5 if the last digit is 0 or 5. 5.A number is divisible by 9 if the sum of its digits is divisible by 9. 6.A number is divisible by 10 if the last digit is 0.

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Definitions Prime Numbers Prime Numbers: A whole number greater than 1 that has only 1 and itself as factors. Composite Numbers Composite Numbers: A whole number greater than 1 that has at least one factor besides itself and 1.

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Prime Factorization Prime Factorization Prime Factorization: Every composite number can be expressed as a product of only prime numbers. Examples: 6 2 3 100 10 10 2 5 2 5 12 3 4 3 2 2 6 = 2 312 = 2 2 3 25 = 2 5 2 5

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Choose all of the prime numbers listed above by clicking on them. You’ll hear chimes and the number will flash if you are correct. 123457911681012 131517192123141618202224

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Choose, by clicking, all of the composite numbers. You’ll hear chimes and the number will flash if you are correct. 123456781091112

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