Factor them.
3 x 5 = 15
2 x 2 x 3 x 5 = 60
Select the common factors.
3 x 5 = 15, the GCF.
The greatest common factor of 15 and 105 is 15.
3
15
It is: 15
The GCF is 15.
The Greatest Common Factor (GCF) is: 15
The greatest common factor of 15 and 32 is 1
The greatest common factor of 15 and 55 is 5.
The greatest common factor for 15 and 16 is 1.
The greatest common factor of 15 and 110 is 5.
3 is the greatest common factor of 69 and 15.
There cannot be a greatest common factor (GCF) of just one number. To be common there need to be at least two numbers. If you find all the factors of two or more numbers, and you find some factors are the same ("common"), then the largest of those common factors is the Greatest Common Factor.