1. 4-2 Factors and Prime Factorization Course 1 Lesson Presentation Lesson Presentation

2. Learn to write prime factorizations of composite numbers. Course 1 4-2 Factors and Prime Factorization

3. Vocabulary factor prime factorization Insert Lesson Title Here Course 1 4-2 Factors and Prime Factorization

4. Course 1 4-2 Factors and Prime Factorization Whole numbers that are multiplied to find a product are called factors of that product. A number is divisible by its factors. 23 6 = Factors Product 2 63 ÷ = 6÷2 = 3 6 is divisible by 3 and 2.

5. Course 1 4-2 Factors and Prime Factorization When the pairs of factors begin to repeat, then you have found all of the factors of the number you are factoring. Helpful Hint

6. Course 1 4-2 Factors and Prime Factorization Additional Example 1A: Finding Factors List all factors of 16. Begin listing factors in pairs. 16 = 1 16 16 = 2 8 1 is a factor. 2 is a factor. 16 = 4 4 3 is not a factor. 4 is a factor. 5 is not a factor. 6 is not a factor. 7 is not a factor. 16 = 8 2 8 and 2 have already been listed so stop here. The factors of 16 are 1, 2, 4, 8, and 16. 1244168 You can draw a diagram to illustrate the factor pairs.

7. Course 1 4-2 Factors and Prime Factorization Additional Example 1B: Finding Factors List all factors of 19. Begin listing all factors in pairs. 19 = 1 1919 is not divisible by any other whole number. The factors of 19 are 1 and 19.

8. Course 1 4-2 Factors and Prime Factorization Check It Out: Example 1A List all factors of 12. Begin listing factors in pairs. 12 = 1 12 12 = 2 6 1 is a factor. 2 is a factor. 3 is a factor. 4 and 3 have already been listed so stop here. 12 = 4 3 1243126 The factors of 12 are 1, 2, 3, 4, 6, and 12 12 = 3 4 You can draw a diagram to illustrate the factor pairs.

9. Course 1 4-2 Factors and Prime Factorization Check It Out: Example 1B List all factors of 11. Begin listing all factors in pairs. 11 = 1 1111 is not divisible by any other whole number. The factors of 11 are 1 and 11.

10. Course 1 4-2 Factors and Prime Factorization You can use factors to write a number in different ways. Factorization of 12 2 61 123 43 2 2 The prime factorization of a number is the number written as the product of its prime factors. Notice that these factors are all prime.

11. Course 1 4-2 Factors and Prime Factorization You can use exponents to write prime factorizations. Remember that an exponent tells you how many times the base is a factor. Helpful Hint

12. Course 1 4-2 Factors and Prime Factorization Additional Example 2A: Writing Prime Factorizations Method 1: Use a factor tree. Choose any two factors of 24 to begin. Keep finding factors until each branch ends at a prime factor. 24 212 6 2 2 3 24 6 4 322 2 24 = 2 2 2 3 24 = 3 2 2 2 The prime factorization of 24 is 2 2 2 3, or 2 3 3. Write the prime factorization of 24.

13. Course 1 4-2 Factors and Prime Factorization Additional Example 2B: Writing Prime Factorizations Method 2: Use a ladder diagram. Choose a prime factor of 45 to begin. Keep dividing by prime factors until the quotient is 1. 345 3 1 15 5 5 45 = 3 3 5 545 3 1 9 3 3 45 = 5 3 3 The prime factorization of 45 is 3 3 5 or 3 2 5. Write the prime factorization of 45.

14. Course 1 4-2 Factors and Prime Factorization In Example 2, notice that the prime factors may be written in a different order, but they are still the same factors. Except for changes in the order, there is only one way to write the prime factorization of a number.

15. Course 1 4-2 Factors and Prime Factorization Check It Out: Example 2A Write the prime factorization of 28. Method 1: Use a factor tree. Choose any two factors of 28 to begin. Keep finding factors until each branch ends at a prime factor. 28 214 72 28 7 4 2 2 28 = 2 2 7 28 = 7 2 2 The prime factorization of 28 is 2 2 7, or 2 2 7.

16. Course 1 4-2 Factors and Prime Factorization Check It Out: Example 2B Write the prime factorization of 36. Method 2: Use a ladder diagram. Choose a prime factor of 36 to begin. Keep dividing by prime factors until the quotient is 1. 336 2 1 12 6 2 36 = 3 2 2 3 The prime factorization of 36 is 3 2 2 3, or 3 2 2 3. 336 3 1 12 2 4 36 = 3 3 2 2 3 3 2 2

17. Lesson Quiz List all the factors of each number. 1. 22 2. 40 3. 51 1, 2, 4, 5, 8, 10, 20, 40 1, 2, 11, 22 Insert Lesson Title Here 1, 3, 17, 51 Course 1 4-2 Factors and Prime Factorization Write the prime factorization of each number. 4. 32 5. 120 2525 2 3  3  5