How do I find the greatest common factor of 54, 81, and 135? I don't understand the tree diagram either. :(

Answer 1

I usually start with the factors of the largest number. The obvious factor of 135 is 5. Bingo! 5 * 27 = 135

27 is also a factor of 81 and 54.

This site explains the factor tree.

http://www.mathsisfun.com/definitions/factor-tree.html