Greatest common factor 84 and 100

4

Step-by-step explanation:

The factors of 84 are: 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84

The factors of 100 are: 1, 2, 4, 5, 10, 20, 25, 50, 100

They have 4 in common

4

Step-by-step explanation:

100 = 2*2*5*5

84 = 2*2*3*4

the greatest common factor is a prime number whit most appearance in both numbers:

in this case the prime number is 2 and it is repeated twice in both numbers, hence 2*2 = 4