1. Warm UP Step 1: Write the whole numbers from 2 through 48. Step 2: Circle 2 and cross out all multiples of 2 other than 2 (the first row below is shown for you) Step 3: Then go to the next remaining number after 2, circle it, and cross out all its multiples other than itself. Step4: Repeat until every number is either circled or crossed out.

2. Prime and Composite Numbers A prime number is a number greater than 1 whose only whole number factors are and itself. A composite number is a whole number greater than 1 that has whole number other than 1 and itself. The number is neither prime nor composite. 1 factors 1

3. Writing Factors of a Number Field Trip: A class of 36 students is on a field trip at the aquarium. The teacher wants to break the class into groups of the same size. Find all possible group sizes by writing all of the of 36: factors

4. Identifying Prime and Composite Numbers Ex: Tell whether the number is prime or composite: 1.56 1.11 List the Factors: 56 = 1 x 56 = 2 x 28 = 4 x 14 = 7 x 8 List the Factors: 11 = 1 x 11

5. Prime Factorization & Factor Trees Prime Factorization: to factor a whole number as a of prime numbers. You can use a tree. Use an when a prime number factor appears more than once. Ex: Use a factor tree to write the prime factorization of 54: product factor exponent Both factors trees = 2 x 3 x 3 x 3 = 2 x 3 3

6. Greatest Common Factor (GCF) Common Factor : a whole number that is a factor of two or more whole numbers Greatest Common Factor (GCF): the of the common factors, which can be found two ways: 1. Making a list of all factors: Ex: Find the GCF of 48, 24, and 36: nonzero greatest

7. Greatest Common Factor (GCF) 2. Use prime factorization: Ex: Find the GCF of 180 & 126

8. Guided Practice 1. Write all the factors of the number and tell whether it is prime or composite: a) 35 b) 65 c) 47 2. Use a factor tree to write the prime factorization of the number: 48 3. Find the GCF of 16 and 28 by listing the factors: 4. Find the GCF of 90 and 150 by using prime factorization 1, 5, 7, 35; Composite 1, 5, 13, 65; Composite1, 47; Prime 2 4 x 3 16: 1, 2, 4, 8, 16 28: 1, 2, 4, 7, 14, 28 The GCF is 4 30