1. Least Common Multiple
Algebra Seminar

2. What is LCM? LCM stands for Least Common Multiple
LCM is used to find a common denominator for two fractions in order to compare them.
LCM is defined as: the smallest number that both numbers are factors of.
Lets watch a short video from on LCM.

4. Finding the LCM Least Common Multiple (LCM):
Method 1: Make a list of multiples
Ex: Find the LCM of 4 and 9
9: 9, 18, 27, 36, 45,
4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40 44
36 is the LCM of 4 and 9

5. More Examples of LCM Ex: Find the LCM of 10 and 12
10, 20, 30, 40, 50, 60, 70, 80, 90, 100
10:
12:
12, 24, 36, 48, 60, 72, 84, 96, 108
60 is the LCM of 10 and 12
Ex: Find the LCM of 6 and 8
6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72 6: 8:
8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88
24 is the LCM of 6 and 8

6. Tips for finding the Least Common Multiple
1. Make a list of multiples for each number 2. Look for the smallest number they have in common 3. If you are looking for the LCM of more than two numbers make more lists. The LCM must be common to ALL of the numbers.
5 = 5, 10, 15, 20, 25, 30, 35
6 = 6, 12, 18, 24, 30, 36
10 = 10, 20 , 30, 40, 50 , 60

7. Using the LCM to Put Fractions in Order
Put the following fractions in order from greatest to least without using a calculator:
Without a calculator, we cannot change the fractions to decimals. We will have to use LCM.

8. Using the LCM to Put Fractions in Order
Step 1: Find the LCM of the denominators

9. The LCM of 6, 12, 9, and 3 is….
6: 6, 12, 18, 24, 30, 36, 42, 48…
12: 12, 24, 36, 48 …
9: 9, 18, 27, 36, 45 …
3: 3, 6, 9, 12, 15, 18, 21, 24, 27
30, 33, 36, 39, 42 …
LCM = 36

10. 6 21 36 36 20 24 36 36 Step 2: Write equivalent fractions. x 6 x 3 x 6

11. 21 6 36 36 24 20 36 36 Step 3: Compare the numerators
Greatest to Least 21 6 36 36 24 20 36 36

12. Put the Fractions in Order
Now try this one.

13. Here are some more to try.
The correct answer is:
Here are some more to try.