Transcript Least Common Multiple (LCM)

Least Common Multiple
(LCM)
Created by: Mrs. J Couch
Least Common Multiple
 Finding the least (lowest) multiple that two (or more)
numbers have in common
Finding LCM using
Ladder Method
Divide out all the common factors down the left side.
LCM=
What number
(smallest prime #)
goes into both
Does
#
24
andany
60?
besides 1
go into both
How about
12 and 30?
6 and 15?
Anything else?
No?
You’re done.
Multiply “L” to
get LCM
LCM using prime factorization
Prime Factorization
(put in columns based
on the number):
24: 2 2 2 3
36: 2 2
3 3
2 2 2 3 3 = 72
(name each column and multiply the names to get LCM)
Practice
 Find the LCM of 6 and 12
Practice
 Find the LCM of 8 and 10
Practice
 Find the LCM of 8 and 12
Practice
 Anna buys dog food every 6 days and cat food every 9
days. If she buys both kinds of pet food today, in how
many days will she next buy both kinds of pet food?
Practice
 You and your friends have tickets to attend a music
concert. While standing in line, the promoter states he
will give a free album download to each person that is a
multiple of 2. He will also give a backstage pass to
each fourth person and floor seats to each fifth person.
Which person will receive the free album download,
backstage pass, and floor seats?
Practice
 What is the least common multiple of 3, 8, and 12?
Exit Slip
1.) The Parents Teachers Association (PTA) at your
school donated school supplies to help increase student
creativity and student success in the classroom. Your
teacher would like you to create kits that include one
package of colored pencils, one glue stick, and one ruler.
When you receive the supplies, you notice the colored
pencils are packaged 12 boxes to a case, the rulers are
packaged 30 to a box, and glue sticks are packaged 4 to
a box.
What is the smallest number of each supply you will need
in order to make the kits and not have supplies left over?
2.) What is least common multiple of 9 and 12?