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Definition:
Least Common Multiple (LCM) – Is the smallest multiple that
two or more numbers have in common.
Method 1: Finding The LCM by Listing the Multiples
Example 1: Find the LCM of 5 and 7 by listing the multiples.
Multiples of 5: 5, 10, 15, 20, 25, 30, 35
Multiples of 7: 7, 14, 21, 28, 35, 42
35 is the least common multiple of 5 and 7 because it is the
smallest number that both numbers go into.
Method 2: Finding The LCM by Using a Table
Example 2: Find the Least Common
Multiple of 12 and 10.
Prime
Numbers
2
10
12
2
5
6
3
5
3
5
5
1
1
2 • 2 • 3 • 5 = 60
Multiply the prime numbers.
60 is the LCM of 12 and 10.
Method 2: Finding The LCM by Using a Table
Example 3: Find the Least Common
Multiple of 4, 5 and 9.
Prime
Numbers
2
4
5
9
2
2
5
9
3
1
5
9
5
3
3
5
5
1
1
2 • 2 • 3 • 3 • 5 = 180
Multiply the prime numbers.
180 is the LCM of 4, 5 and 9.
Find the least common multiple of the following sets of numbers by
using a table.
1.) 5 and 16
2.) 5, 9 and 12
3.) 12, 15 and 20
Real-Life Application
Gabe has painting class every two weeks. Navpreet has a pottery
class every five weeks. Gabe and Navpreet met at the art building
for class this week. How many weeks will it be until they see each
other again at the art building?