The Greatest Common Factor also known as GCF is the largest number that can divide equally into two or more numbers.
For the problem they ask 'Which number pair has a 'GCF' of 6.
First let's look at the answer choice 'A' that gives us 18 and 54.
Now for this we need to list the factors of both 18 and 54. A factor being a number that can be multiplied by another number to get the sum.
18: 1, 2, 3, 6, 9, 18
54: 1, 2, 3, 6, 9, 18, 27, 54
So right away we can see the the largest number that can be divided into both of them equally is not 6, it is 18. This means we can mark out A as a possible answer.
Next let's try B and list the factors of both 30 and 42.
30: 1, 2, 3, 5, 6, 15, 30
42: 1, 2, 3, 6, 7, 14, 21, 42
Looks like we found our answer! The largest factor they have in common is 6!
I'm still going to go ahead and list the GCF's for answers C and D.
