Ladder Method to Solving GCF & LCM
GCF = 2 x 2
Find the GCF and LCM of 8 and 12.
LCM =

4 x 2 x 3
1. Put the two numbers inside the
 "ladder".

2. What is the smallest number that
will divide evenly into both
numbers.

3. Write how many times it will
divide into each below the line.

4. Repeat steps 2 and 3 until there
are prime numbers left.

5. GCF is the product of all factors
on the left.

6. LCM is the product of the GCF
and the numbers remaining.
STEPS:
Find the GCF and LCM of 4 and 10.
LCM =
GCF =
Note: When the smaller number divides into the
larger number evenly, the answers are the same
as the original problem.

Find the GCF and LCM of 5 and 10.
LCM =
GCF =
Find the GCF and LCM of 4 and 12.
LCM =
GCF =
NOTE: Sometimes, the only number that will divide
into both of the numbers is 1.
Find the GCF and LCM of 12 and 7.
LCM =
GCF =
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