PERT Practice Test 2025 – Complete Guide for Exam Prep

To determine the greatest common factor (GCF) of two numbers, one needs to identify the largest number that divides both of the given numbers without leaving a remainder. This means you're looking for the highest factor that they share in common, which ensures that it divides both numbers evenly.

For instance, if you are finding the GCF of 12 and 16, the factors of 12 are 1, 2, 3, 4, 6, and 12, while the factors of 16 are 1, 2, 4, 8, and 16. In this case, the common factors are 1, 2, and 4. Among these, the largest is 4, which would be the GCF of 12 and 16.

In contrast, merely identifying the smallest number that divides both incorrectly suggests that you're looking for the least common factor, not the greatest, so that option isn't valid. Adding the two numbers or multiplying them does not relate to the concept of finding common factors, as it does not yield any information about divisibility. Thus, recognizing the largest common divisor is the correct approach to finding the GCF.