1. OBJ: to find the greatest common factor of two or more numbers.
Lesson 4.2
OBJ: to find the greatest common factor of two or more numbers.

2. Vocabulary
Common Factor – a whole number that is a factor of two or more nonzero whole numbers.
Greatest Common Factor – the greatest of all common factors.
Relatively Prime – two or more numbers that have a greatest common factor of 1.

3. Finding the GCF Method 1 Method 2
List all the factors of each number. Identify the greatest number that is on every list.
Method 2
Write the prime factorization of each number. The GCF is the product of the common prime factors.

4. Find the GCF 12 and 30 21 and 42 16, 42, and 40 27, 45, 90 18 and 33

5. GCF of Monomials Factor each monomial and find the common factors.
6x and 15x
20x2 and 36x
32y2 and 6x2y
7xy3 and 28xy2

6. Assignments
In class, Text p. 179, #’s 12, 14, 24, 25, 30, 31, 38, 42, and 44
HW – Complete Practice W.S. 4.2 all problems.