1. Name _________________________________________ Date __________________
Mrs. Labuski / Mrs. PortsmorePeriod ______ Fifth Grade Flashback!!
Concept1: FactorTrees & Prime Factorization
To find the Prime Factorization of each number use a Factor Tree
36
1. Choose any two factors of the number: 3 12
2. Circle the prime number 2  6
3. Keep finding factors until each branch ends in a prime number 2 3
4. Rewrite the factors in order 36= 322 3
5. Combine any factors into exponential form 36= 22  32
Now let’s try one together:
1. 28 2. 45
____________________ ____________________
3. 50 4. 72
____________________ ____________________
What divisibility
rule can help you?
____
What divisibility
rule can help you?
____
What divisibility
rule can help you?
____
What divisibility
rule can help you?
____

2. Concept2 GreatestCommon Factor
Use FactorTrees to help you find the Greatest Common Factor of two numbers.
Draw your factor trees
Complete the Venn Diagram.
Multiply the common factors to find the GCF
GCF 𝟑𝟎, 𝟓𝟎 GCF 𝟑𝟎, 𝟒𝟓
GCF: 2 x 5 = 10 GCF: 3 x 5 = 10
GCF= 10 GCF = 15
Now you try:
1- factor trees
2 – Venn diagrams
GCF 𝟒𝟓, 𝟔𝟎 GCF 𝟒𝟐, 𝟕𝟎

3. Concept3 GCF & Distributive
Example: 36 + 8 as 4(9 + 2).
Step 1: Find the GCF of the numbers in the sum. GCF of 36 and 8 is 4.
Step 2: Replace each number by a productof the GCF and its other factor.
36 + 8 = 4

 9 + 4

 2
Step 3: Replace the sum of the products bytwo factors with the GCF as a multiple of the sum of
two whole numbers. 36 + 8 = 4

 9 + 4

 2 = 4(9 + 2)
Write each of the following sums as two factors of their GCF and a sum:
1) 24 + 16 (GCF=_4____) 2) 25 + 15 (GCF=_____) 3) 35 + 28 (GCF=_____)
___4(6+4)_____ _______________ ________________
4) 63 + 54 (GCF=_____) 5) 80 + 30 (GCF=_____) 6) 12 + 9 (GCF=_____)
______________ _______________ ________________
7) 54 + 36 (GCF=_____) 8) 49 + 84 (GCF=_____) 9) 24 + 18 (GCF=_____)
______________ _______________ ________________
10) 20 + 44 11) 4 + 12 12) 6 + 8
______________ _______________ ________________

4. Concept 1 Answer Key
Now let’s try one together:
2. 28 2. 45
2 14 5 9
2 7 3 3
22 7 32 5
3. 50 4. 72
5 10 8 9
2 5 2 4 3 3
2 2
2  52 23  32
Concept 2 Answer Key
GCF 𝟒𝟓, 𝟔𝟎 GCF 𝟒𝟐, 𝟕𝟎
GCF: 3 x 5 = 15 GCF: 2 x 7 = 14
GCF= 15 GCF = 14

5. Concept3 Answer Key
Write each of the following sums as two factors of their GCF and a sum:
1) 24 + 16 2) 25 + 15 3) 35 + 28
4(6+4) 5(5+3) 7(5+4)
4) 63 + 54 5) 80 + 30 6) 12 + 9
9(7+6) 10(8+3) 3(4+3)
7) 54 + 36 8) 49 + 84 9) 24 + 18
18(3+2) 7(7+12) 6(4+3)
10) 20 + 44 11) 4 + 12 12) 6 + 8
4(5+11) 4(1+3) 2(3+4)

6. Name _______________________________________ Date ____________________
Mrs. Labuski / Mrs. PortsmorePeriod ________ FlashBack Homework
Concept1 & 2
Directions – Use Factor Trees & Venn Diagrams to find the GCF.
1) 36 and 60
2) 75 and 125
Concept3 GCF & Distributive
Write each of the following sums as two factors of their GCF and a sum:
1) 22 + 16 (GCF=_____) 2) 35 + 20 (GCF=_____) 3) 32 + 28 (GCF=_____)
______________ _______________ ________________
4) 63 + 45 (GCF=_____) 5) 70 + 40 (GCF=_____) 6) 18 + 42 (GCF=_____)
______________ _______________ ________________
7) 54 + 18 (GCF=_____) 8) 49 + 98 (GCF=_____) 9) 51 + 18 (GCF=_____)
______________ _______________ ________________
10) 24 + 40 11) 20 + 24 12) 49 + 63

7. ______________ _______________ ________________