Never. 8 can never have a factor greater than itself. Thus, the gcf is 8
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
The GCF is 8.
Same as the gcf of 32 and 8 (8 is the remainder of the division of 40 by 32).