What is the greatest common factor of 84 and 156?

Answer: 12

Definition: A factor is a divisor - a number that will evenly divide into another number. The greatest common factor of two or more numbers is the largest factor that the numbers have in common.

Method:

One way to determine the common factors and greatest common factor is to find all the factors of the numbers and compare them.

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

The factors of 156 are 1, 2, 3, 4, 6, 12, 13, 26, 39, 52, 78, and 156.

The common factors are 1, 2, 3, 4, 6, and 12. Therefore, the greatest common factor is 12.