The GCF is 9.
The GCF is 18.
The GCF is 8.
The GCF is 6.
The GCF is 8.
The GCF is 9.
It is 3
The GCF is 8.
The GCF is 8.
The GCF is 4.
The GCF is 1.
To find the GCF of two (or more) numbers, factor them , and see which numbers are common to both strings of numbers, and reduce the 'string' to '1'. Hence 2)42 3)21 7)7 = 1 & 2)72 2)36 2)18 3)9 3)3 = 1 Hence one lot of '2' is common to both numbers. Similarly one lot of '3' is common to both numbers. Hence 2 x 3 = 6 is the GCF of '42' & '72'. NB THe other 2's and the '3' and '7' are NOT common factors as they do NOT appear in both strings of numbers.
The GCF is 12.