What is the Greatest Common Factor? (GCF)

The greatest common factor (GCF) is the largest number that divides evenly into the given numbers.

Here’s an example.

  • What’s the GCF of 12 and 24?
  • We’re looking for the largest number that divides evenly into 12 and 24.
  • In this case it would be 12.

We will show you how to use factor trees to figure this out for larger numbers where the answer is not so easy to find.

What is the Least Common Multiple? (LCM)

The least common multiple (LCM) is the smallest number that is a multiple of the given numbers.

Let’s look at an example.

  • Say we are looking at the numbers 2 and 3.
  • Let’s list some multiples of each:
    • Multiples of 2: 2, 4, 6, 8, 10
    • Multiples of 3: 3, 6, 9, 12, 15
  • The smallest number that is a multiple of both 2 and 3 is 6.
  • Therefore, the LCM of 2 and 3 is the number 6.