1. 5.6 – Least Common Multiple
MJ2A
5.6 – Least Common Multiple

2. Bellwork Add or subtract. Write your answer in simplest form. 1 + 1

3. Assignment Review
Text p. 235 # 11 – 30

4. Before we begin… Please take out your notebook and get ready to work…
Today we will look at the Least Common Multiple (LCM) of 2 or more numbers…
For those students that do not know their multiplication tables…knowing this will help you when you have to convert fractions to a common denominator
Raise your hand if you can tell the class what a least common multiple is…

5. Objective 5.6
Students will find the least common multiple of two or more numbers.

6. Least Common Multiple
A multiple of a number is the product of that number and a whole number.
Example:
5 x 0 = 0
5 x 1 = 5
5 x 2 = 10 etc…
We can say that the multiples of 5 are 0, 5, 10, 15, etc…
As the name suggests the least common multiple of 2 or more numbers is the smallest multiple that the numbers have in common.

7. Finding the LCM
There are a number of methods that can be used to find the LCM.
You can:
List the multiples of each number
Do a factor tree
Use the cake method
For today’s lesson we will look at the cake method as that is the easiest method…

8. Example Find the LCM of 4 and 6 2 4, 6 2 3 The LCM will be 2x2x3 = 12
2 4, 6
2 3
The LCM will be 2x2x3 = 12
Notice that the numbers form the shape of an L to help you remember what to multiply

9. Example Find the LCM of 16 & 24 2 16, 24 2 8 12 2 4 6 2 3
2 16, 24
2 3
The LCM is 2 x 2 x 2 x 2 x 3 = 48

10. How does this help with Common Denominators?
Knowing the LCM can help you with finding a common denominator when adding or subtracting unlike fractions
In the previous example suppose you were adding 8/16 & 3/24, you could use the cake method to find the LCM and therefore, know that the smallest number that both 16 and 24 go into is 48
When using the LCM you minimize the need to simplify the fractions

11. Your Turn
In the notes section of your notebook write and find the LCM of the following:
6 & 8
12 & 30
10 & 14

12. LCM of Monomials
You can also use the cake method to find the LCM of algebraic monomials
Find the LCM of 12b2 & 8ab
2b 12b2, 8ab
2 6b 4a
3b 2a
The LCM = 2b x 2 x 3b x 2a = 24ab2

13. Your Turn
In the notes section of your notebook write the monomials and then find the LCM of each
12x2y2 & 6y3
15b2 & 25b3

14. Summary
In the notes section of your notebook summarize the key concepts covered in today’s lesson.
Today we discussed
LCM – what is it?
Name 3 methods to find the LCM
How can knowing LCM help you with unlike fractions?

15. Assignment Practice Skills workbook lesson 5.6 Reminder
This assignment is due tomorrow
I do not accept late assignments
Do the odd problems only
Write them on a separate sheet of paper and show how you got your answer (no work = no credit)