Least common multiple

Least Common Multiple

LCM

Important vocabulary

• multiples- products of a number when multiplied by 1, 2, 3, 4,

• least- smallest, lowest

• common- the same number that appears in both numbers.

• Least common multiple (LCM)- the smallest multiple that 2 or more numbers have in common.

Steps to find the LCM

1. List multiples of each number Make sure you have correct multiples. (x1, x2 ,x3, etc.)

[Start with the larger number and find the first 5-6 multiples]. Then find the multiples of the smaller number.

2. When you get to the first number that is the same in both, you have found the LCM.

3. Write all work in neat orderly way.

2 ways to find the LCM.

1. List all the multiples and find the smallest multiple.

2. Prime factorization - factor tree

Poll

When finding LCM you must write all the factors of each number?

• True

• False

Find the LCM of each set of numbers.

LCM of 9 and 12

12 = 12, 24, 36, 48, 60...

9 = 9, 18, 27, 36
 
LCM = 36

1.) Find LCM of 2 and 3

3 = 3, 6, 9, 12, 15....

2 = 2, 4, 6

LCM= 6

2.) Find the LCM of 12 and 24

Prime factorization- breaking down a composite number into its prime factors. (factor tree)

Find the prime factorization of 24. There is more than one way to start prime factorization. The next slide shows how you can find the prime factorization of 24.

Find the prime factorization of 60.

Find the prime factorization of 42.