1. We can find a multiple by multiplying the numbers together, but to find the Least Common Multiple we have to get rid of any factors that the numbers have in common.

2. What’s the LCM of 4 and 6? Multiples of 4: 4, 8, 12, 16, 20, 24 ….

3. How can we find the LCM without listing multiples
How can we find the LCM without listing multiples? How can we “get rid of” the factor(s) that 4 and 6 have in common?
Use Prime Factors

4. Prime factors of 4: 2 X 2 Prime factors of 6: 2 X 3
What do they have in common?
Get rid of the second one.
Now multiply what you have left
2 X 2 X 3 = 12

5. Here’s how this works:
Find the Least Common Multiple of
18 and 27. 18 27
Find prime
factors. 3 9 2 9 3 3 3 2 3 3

6. 18 = 2 X 3 X 3 27 = 3 X 3 X 3 Find common factors.
Get rid of the extras of each repeated factor.
Multiply what’s left -
2 X 3 X 3 X 3 = 54

7. 54 is the
Least Common Multiple
of 18 and 27.