Answer:
Factors of 16 : 1 , 2 , 4 , 8 , 16
Factors of 20 : 1 , 2 , 4, 5 , 10 , 20
They both have 1 , 2 and 4 as their common factors.
You're going to choose between the two numbers , which is greater?
So, 4 is the greatest common factor of 16 and 20.
