The greatest common factor (GCF) of 28 and 32 is: 4
To find the GCF we have to list the factors of each number we are given. In this case, 28 and 32 is our numbers we have to list factors from. Our minimum factor is the original number we started with.
Factors of 28: 1, 2, 4, 7, 14, 28
Factors of 32: 1, 2, 4, 8, 16, 32
Find the common factor out of them, and then find the factor with the highest value. The common factors of each numbers are 1, 2, and 4. The highest number out of that is 4, so 4 is our GCF.