1. Least Common Multiple
Objective: To find the least common multiple
Vocabulary:
Least Common Multiple (LCM):
The least non-zero common multiple of two or more numbers.
Method 1: Make a list of multiples
Ex: Find the LCM of 4 and 9
4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44 4: 9:
9, 18, 27, 36, 45,
36 is the LCM of 4 and 9

2. Method 2: Prime factorization with factor trees.
Find the LCM of 10 and 12 10 12 4 2 2 3 5 2
10 = 2 • 5
Multiply the factors, using the common factors only once
12 = 2•2•3
2•2•3•5 =

3. Method 3: prime factorization using upside-down division
Find the LCM of 12 and 16 2 12 2 16 2 6 2 8 3 2 4 2
12 =
16 =
2•2 • 3
Multiply the factors using the common factors only once.
2•2•2•2
2•2•2•2•3= 48

4. Find the LCM of 24 and 84 2 2
No more common factors
2•2•6•7 = 168

5. 88 180 120 225 Find the LCM of the following 1) 8 and 22 2) 18 and 20

7. You are having a barbeque and will be serving hot dogs
You are having a barbeque and will be serving hot dogs. You notice that hot dogs are sold in packs of 6 and hot dog buns are sold in packs of 8. You want to have the same number of hot dogs as buns without any left over. How many packs of each should you buy?
Hot Dogs: 6: 6, 12, 18, 24, 30, 36
HD Buns: 8: 8, 16, 24, 32,40
4 packs of Hot Dogs
3 packs of Buns