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Chapter/Lesson: Chapter 3 Lesson 1 Page: 104
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Objective/Title: Factors and Prime Numbers
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Important Terms
Quick Solve
Factor: one of the numbers that is
multiplied to give a product
Prime number: 1 and itself (5: 1 × 5 or 1, 5)
Composite number: 1, itself, and at least
one other # (10: 1 × 10, 2 × 5 or 1, 2, 5, 10)
Prime Number: having only 2 factors
one and itself
Find factors by listing the pairs of #'s that
multiply to give the product you are
looking for. Example:
What are the factors of 12?
1 × 12
2×6
3×4
Composite Number: having more than 2
factors one, itself, and at least one other
number
*0 and 1 are neither prime nor composite
Practice Questions
List all factors pairs for each number, then identify each number as prime or composite.
1.
12
Prime Composite
1, 2, 3, 4, 6, 12
3.
32
Prime Composite
5.
11
Prime Composite
7. 48 Prime Composite
9.
2.
21
Prime Composite
1, 2, 4, 8, 16, 32 4.
50
Prime Composite
1, 11
36
Prime Composite 1, 2, 3, 4, 6, 9, 12, 18, 36
6.
Prime Composite
1, 2, 3, 6, 9, 18
11. 31
Prime Composite
1, 31
13. 86
Prime Composite 1,2, 43, 86
15. 17
Prime Composite
1, 17
1, 2, 5, 10, 25, 50
8.
51
Prime Composite
10.
30
Prime Composite 1, 2, 3, 5, 6, 10, 15, 30
1, 2, 3, 4, 6, 8, 12, 16, 24, 48
18
1, 3, 7,21
12.
25
14. 24
16. 37
Prime Composite
1, 3, 17, 51
1, 5, 25
Prime Composite 1, 2, 3, 4, 6, 8, 12, 24
Prime Composite
1, 37
Notes and Examples
Using the Sieve of Eratosthenes (a mathematician who developed this process), we can
identify all prime numbers from 1-100
*1 is neither prime nor composite
*Prime numbers are circled
*Composite numbers are crossed off
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
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75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Prime Number: 5 is prime because only 2 numbers can be multiplied together to get a
product of 5 (1 × 5 = 5.) You can't multiply any other numbers together and get a
product of 5. This means that 1, 5 are the only factors of 5.
Composite Number: 4 is composite because you can multiply 1 × 4 to get a product of
4, also 2 × 2 to get a product of 4. This means that 1, 2, 4 are all factors of 4.
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