1. 07 GCF using Prime Factors Do “07 Warmup GCF with Prime Factors” in clicker (CPS) database. I know how to do prime factorization (factor trees) A=Yes B=No 20 45 22 Example : x x Circle if Prime 20 = 2 x 2 x 5

2. Find GCF 1 st Make Factor Trees for both #’s 2 nd List the prime factors in order for each # 3 rd Multiply the common pairs That’s the GCF !

3. Example GCF(12,20) = 20 45 22 x x Circle if Prime 12 = 2 x 2 x 3 12 43 22 x x 20 = 2 x 2 x 5 Make common pairs x22= 4

4. Another Example GCF(12,18) = 12 = 2 x 2 x 3 18 = 2 x 3 x 3 x23= 6

5. Another Example GCF(12,24) = 12 = 2 x 2 x 3 24 = 2 x 2 x 2 x 3 x23 = 12 x2 Notice the GCF is one of the #’s !