You need at least two numbers to find a GCF.
First you find the factors of 45 and 60. The Factors of 45 are:1,3,5,9,15,and 45 The Factors of 60 are:1,2,3,4,5,6,10,12,15,20,30,60 The GCF is the highest common number so the GCF is 15.
The GCF is 3.
The GCF is 15.
The GCF is 10.
The GCF is 12.
The GCF is 2.
The GCF is 15.
GCF: 12
The GCF is 4.
The GCF is 6.
The GCF is 20.
4 is the greatest common factor. The common factors are 1,2, and 4.