**How do I calculate the GCF (or LCM) of 3 or more numbers?**- Calculate the GCF (or LCM) of the first two numbers. Then calculate the GCF (or LCM) of the answer to the first calculation and the third number. Continue using the previous answer with the next number in your list until your list is exhausted. GCF(a,b,c)=GCF(GCF(a,b),c) and LCM(a,b,c)=LCM(LCM(a,b),c)

Bill von Ofenheim