The greatest common factor of these numbers is 18.
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<em>Comment on the GCF</em>
It can be useful to know Euclid's algorithm for finding the GCF:
Determine the remainder from dividing the larger number by the smaller.
If the remainder is zero, the smaller number is the GCF. If the remainder is non-zero, use it to replace the larger number and repeat from step 1.
For example, 126 mod 90 = 36; 90 mod 36 = 18; 36 mod 18 = 0, so 18 is the GCF of 126 and 90. (The modulo function 'mod' returns the remainder from division.)
