Find the gcf of 72 and 80

One way to I solve this is by listing all the ways it can be multiplied by:

72: 1*72, 2*36, 3*24, 4*18, 6*12, 8*9.

80: 1*80, 2*40, 4*20, 5*16, 8*10.

Group the factors that they have in common.

Which are 1, 2, 4, and 8.

After that, find the greatest common factor that they both share.

Answer: 8