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