Today's topic is factors and greatest common factors. Let's start with factors. Your vocabulary for factor lesson is the word factor. A factor is a number that divides evenly into another number. How do you find them? The number one is a factor of every number. Two is a factor if the number is even. Three is a factor if the sum of the numbers in the number are divisible by three. Four is just divide by two twice. Five is a factor if the number ends in 0 or 5. Six if the number is divisible by 3 and 2. Sevens are hard because it is a prime number. Eight is factor if you can divide it by four twice. Nine if the sum of the digits is divisible by 9. Ten if it the number ends in 0. The hard part is finding the factors other factor. You do this by dividing the factor into the number that your trying to find out the other factor of.  That's factors.To find the GCF you must write out all the factors of the two numbers to find the GCF. The highest idenitical factor of the set is the GCF. That's the GCF. Here are two cool links. http://www.helpwithfractions.com/greatest-common-factor.html and http://amby.com/educate/math/2-1_GCF.html