Download GCF and LCM Topic 3

Topic #3: GCF and LCM
What is the difference between a
factor and a multiple?
List all of the factors and the first
3 multiples of 6.
Example: Find the GCF of 6 and 21.
The GCF is 3.
Example: Find the LCM of 6 and 21.
The LCM is 42.
When looking for the GCF of terms
with variables, choose the
smallest power of each variable.
Example: Find the GCF of x5 and x3.
The GCF is x3.
When looking for the LCM of terms
with variables, choose the largest
power of each variable.
Example: Find the LCM of x5 and x3.
The LCM is x5.
 Find
 6x
the GCF and LCM
and 3
GCF = 3
LCM = 6x
 Find
 12x
the GCF and LCM
and 15xy
GCF = 3x
LCM = 60xy
 Find
the GCF and LCM
 10x2y
and 15xy2
GCF = 5xy LCM = 30x2y2
How will you remember
the difference between a
GCF and an LCM?
Find the GCF and LCM
2 and 6
GCF = 2
LCM = 6
3 and 4
GCF = 1
LCM = 12
12 and 18
GCF = 6
LCM = 36
Find the GCF of 3xy3 and 15x4y2.
Find the LCM of 3xy3 and 15x4y2.
GCF and LCM
Greatest Common Factor (GCF) – the
GCF of two numbers is the biggest factor
they have in common. In other words, the
biggest number that divides evenly into
both numbers.
Example: Find the GCF of 6 and 21.
Factors of 6: 1, 2, 3, 6
Factors of 21: 1, 3, 7, 21
GCF is 3.
GCF and LCM
Least Common Multiple (LCM) – the
smallest multiple that two or more numbers
have in common.
Example: Find the LCM of 6 and 21.
Multiples of 6: 6, 12, 18, 24, 30, 36, 42, 48…
Multiples of 21: 21, 42, 63…
LCM is 42.