To find the greatest common factor (GCF) of the numbers 21, 15, and 30, you can first find the common factors of these numbers and then determine the largest one.
Let's find the factors of each number:
Factors of 21: 1, 3, 7, 21
Factors of 15: 1, 3, 5, 15
Factors of 30: 1, 2, 3, 5, 6, 10, 15, 30
Now, let's identify the common factors among these three sets:
Common factors: 1 and 3
The greatest common factor (GCF) of 21, 15, and 30 is 3.