A factor is any number that divides into a larger number evenly. The greatest common factor is the largest number that divides into two (or more) numbers evenly. Greatest Common Factors can be used for reducing fractions and factoring polynomials.
The easiest way to find a GCF is to express each number as a product of primes. Then circle those factors that are common to each number. The greatest common factor is the product of the numbers which are circled.
Example: Find the greatest common
factor of 84 and 120.
Step 1:Factor each number into the product of primes. |
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Step 2:Circle the pairs of factors that each number has in common. |
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Step 3:The GCF is the product of the numbers which are circled, but only
include one factor |
 Thus, the GCF of 84 and 120 is 12. |