Finding the Greatest
Common Factor
Grade 5
Lesson Objectives
• 6.B.1.c Identify the greatest
common factor
3.A.1.a Use technology tools, including
software and hardware, from a range
of teacher-selected options to learn
a new content or reinforce skills
Think Backwards…
• Find Factors
• Circle Common Factors
• Group Greatest Factor
Step 1: Find the Factors
• 24 – 1,2,3,4,6,8,12,24
• 36 – 1,2,3,4,6,9,12,18,36
Step 2: Circle Common
Factors
• 24 – 1,2,3,4,6,8,12,24
• 36 – 1,2,3,4,6,9,12,18,36
Step 3: Group the
Greatest Factor
• 24 – 1,2,3,4,6,8,12,24
• 36 – 1,2,3,4,6,9,12,18,36
The Greatest Common
Factor of 24 and 36
is…
12
Now let’s try finding the
GCF
Find the GCF of 12 and
24
• Step 1: Find the
factors
• 12 – 1,2,3,4,6,12
• 24 –
1,2,3,4,6,8,12,24
Find the GCF of 12 and
24
• Step 2: Circle the
common factors
• 12 – 1,2,3,4,6,12
• 24 –
1,2,3,4,6,8,12,24
Find the GCF of 12 and
24
• Step 3: Group the
greatest factor
• 12 – 1,2,3,4,6,12
• 24 –
1,2,3,4,6,8,12,24
The Greatest Common
Factor of 12 and 24 is
…
12
Your turn!
• Find the Greatest Common Factor of
16 and 20.
• Remember…Find Factors, Circle
Common, Group Greatest!
The Greatest Common
Factor of 16 and 20 is…
4
Are you ready?
Let's try some more!