Lesson 5

Find Prime Factors

Est. Class Sessions: 1

Summarizing the Lesson

Ask students to list all the factors and find the prime factorization of 220. Give student pairs a few minutes to find both the factors and the prime factors of 220. Ask students to write the prime factorization as a number sentence with exponents and to check the factorization using a calculator. See Figure 5 for possible responses. Circulate looking for a variety of ways students verified the prime factorization to share with the class.

Ask:

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  • Is the list of factors the same as the prime factorization? (no)
  • How can you be sure you found all the factors? (Check on a calculator to see whether each number [1, 2, 3, . . . ] divides into 220 evenly. When you repeat a factor, you found them all.)
  • How can you be sure you have the prime factorization? (All the factors are prime and when you multiply it out you get 220.)
  • Did each student start the factor tree the same way? (no)
  • Did each factor tree end the same way? (yes)
Student Guide:
Student Activity Book:
Master:
Finding the factors and prime factorization of 220
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