What is the GCF of 36 and 60?
Common factors are
Hence Greatest Common Factor is
A method of finding GCF and LCM - especially of several numbers if they are larger than usual - is to write the numbers as the product of the prime factors.
In this way we can immediately see which factors are common:
If you have any number written as the product of its prime factors, then you know everything there is to know about that number.