1. PRIME AND COMPOSITE NUMBERS
LESSON 3

2. PRIME NUMBERS
A Prime Number can be divided evenly only by 1, or itself.
EXAMPLES:
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47

3. COMPOSITE NUMBERS
A Composite Number can be divided evenly by numbers other than 1 or itself.
EXAMPLES:
4,6,8,9,10,12,14,15,16,18,20,21,22,24,25,26,27,28,30,32,33,34,35,36,38,39,40

4. FACTORS
A number may be made by multiplying two or more other numbers together.
The numbers that are multiplied together are called factors.
EXAMPLE:

5. FACTORS
A number may be made by multiplying two or more other numbers together.
The numbers that are multiplied together are called factors.
EXAMPLE:
3 X 4 = 12
PRODUCT
FACTOR
FACTOR

6. FACTORS Therefore PRIME numbers have 2 factors: one and itself.
COMPOSITE numbers have more than two factors.
The number ONE only has one factor (1), therefore it is not prime nor composite but SPECIAL.

7. GCF GCF – GREATEST COMMON FACTOR
The GCF is the highest factor that two or more numbers have in common.
EXAMPLE:
The factors of 18 are {1,2,3,6,9,18}
The factors of 24 are {1,2,3,4,6,8,12,24}

8. GCF GCF – GREATEST COMMON FACTOR
The GCF is the highest factor that two or more numbers have in common.
EXAMPLE:
The factors of 18 are {1,2,3,6,9,18}
The factors of 24 are {1,2,3,4,6,8,12,24}
The GCF is 6.

9. PRIME FACTORS Factors that are prime numbers.
When a composite number is written as a product of all of its prime factors, we have the prime factorization of the number.
EXAMPLE: the number 72 can be written as a product of primes as: 72 =2x2x2x3x3 .
The expression "2x2x2x3x3" is said to be the prime factorization of 72.

10. TRY THIS ONE
Find the PRIME factors of 32
SOLUTION:

11. TRY THIS ONE Find the PRIME factors of 32 SOLUTION: 32 4 x 8
2 x x x 2 x 2
= 25

12. LCM LCM – LOWEST COMMON MULTIPLE
A common multiple is a number that is a multiple of two or more numbers.
The common multiples of 3 and 4 are:
0, 12, 24,….

13. LCM
The least common multiple (LCM) of two numbers is the smallest number (not zero) that is a multiple of both.
EXAMPLE:
Multiples of 3: 6,9,12,15,18,21,24,…
Multiples of 4: 8,12,16,20,24,….
LCM of 3 and 4 is:

14. The least common multiple (LCM) of two numbers is the smallest number (not zero) that is a multiple of both.
EXAMPLE:
Multiples of 3: 6,9,12,15,18,21,24,…
Multiples of 4: 8,12,16,20,24,….
LCM of 3 and 4 is: 12