What is the greatest common factor of 40 and 80?

Answer 1

The greatest common factor of 40 and 80 is 40. (Whenever one of a pair of number is a factor of the other larger number, it is the GCF of the two.)

The greatest common factor (GCF) is often also called the greatest common divisor (GCD) or highest common factor (HCF). Keep in mind that these different terms all refer to the same thing: the largest integer which evenly divides two or more numbers.
The GCF is: 40
40

Answer 2

40. 40 goes into both 80 (twice) and 40 (once).

Answer 3

GCF(40, 80) = 40.