GCF

Greatest Common Factor

G6 Topic 3 Lesson 2

What are factors?

• Numbers that you multiply together to make a product

• Products are answers to multiplication problems.

• 3 and 5 are factors of 15 because 3 x 5 =15

• 15 is the product of the FACTORS 3 and 5.

Multiple Choice

What are all of the factors of 12?

• 1 and 12

• 1, 2, 3, 4, & 6

• 1, 2, 3, 4, 6, & 12

• 1, 2, 3, 4, 6, 10, & 12

• 12, 24, 36, 48, 72 , 84...

What are Prime numbers?

• Whole numbers greater than 1 that only have two factors, 1 and itself

• Prime numbers are only divisible by 1 or itself

• Example: 2 is prime because the only two factors are 1 and 2, (1 x 2 = 2): 11 is prime number because the only two factors are 1 and 11 (1 x11=11).

• Can you list the first 10 prime numbers?

Multiple Select

Select all of the numbers that are prime numbers

• 15

• 7

• 9

• 2

• 13

Open Ended

What are the first 10 prime numbers?

Composite Numbers

• Whole numbers greater than 1 that are not prime numbers.

• Composite numbers have more than 2 factors.

• 4 is a composite number because it's factors are 1, 2, and 4.

Prime Factorization

• Can be used to find the GCF and LCM of two numbers.

• Find all of the prime factors of a given number

• There is only one prime factorization of any number.

Greatest Common Factor (GCF)

• The greatest shared factor between two numbers.

• You can use prime factorization as a strategy to find the GCF of 2 numbers.

• The GCF of two numbers will always be the smaller of the two numbers or less

Multiple Choice

Which pair of numbers has a GCF of 8?

• 8, 36

• 40, 80

• 16, 56

• 24, 42

Multiple Choice

What is the Greatest Common Factor of 12 and 18?

• 1

• 3

• 6

• 8

Multiple Choice

What is the GCF of 9 and 15?

• 1

• 3

• 6

• 8

Multiple Choice

Which pair of numbers have a GCF of 3?

• 15 and 27

• 20 and 30

• 45 and 15

• 9 and 18

Multiple Choice

What is the GCF of 12 and 30?

• 2

• 4

• 6

• 8

• 12

Use the GCF and distributive property to rewrite the following expressions

• EXAMPLE: 14 + 21

• GCF of 14 and 21 is 7

• 14 + 21 = (7x 2) + (7 X 3)

• 7(2 + 3)

• 7( 5) = 35 so, 14 + 21 = 35

Open Ended

12 + 30

Open Ended

25 + 45