What is the greatest common factor of 80 and 45?

Answer 1

The GCF of 45 and 80 is 5.

Prime factors:

45 = 5x3x3

80 = 5x2x2x2x2

the only prime factor in both is 5, and so the highest common factor is 5.

Alternative method:

80 mod 45 = 35

45 mod 35 = 10

35 mod 10 = 5

10 mod 5 = 0

so HCF = 5.

Answer 2

The GCF is 5

Answer 3

The greatest common factor (GCF) is 5.