The concept of common factors makes no sense for fractions. This is because every non-zero fraction can divide every other fraction. For example 27/4 = 5/7*189/20 and 9/16 = 5/7*63/80 so 5/7 is a common factor.
The GCF is 1.
The GCF is 4.
The common factors of 4 and 16 are 1, 2, and 4.
The GCF is 4.
The GCF is 4.
The GCF is 4.
The GCF of 16 and 72 is 8. 16/72 can be reduced to 2/9
The GCF is 16.
The GCF is 4.
The GCF is 4.
The GCF is 1.
The GCF is 4.