Question 328714
The easiest way I know that works for most problems is to start with the largest denominator, which is 6.  Then take multiples of 6 until you get one that is divisible by both 4 and 5.  Here we go:  6,12,18,24,30,36,42,48,54,60.  That's it!!  The LCD is 60.  


There are a lot of other ways to teach this, but this way is really helpful in most of the problems you encounter.


For more on common denominators, please see the curriculum that I'm giving away FREE on my own website!  To see this website, click on my tutor name "rapaljer" anywhere in algebra.com.  Click on my website name that you will see there, and look on my Homepage for "Basic, Intermediate, and College Algebra: One Step at a Time."  Choose "Basic Algebra" and look in "Chapter 3" for "Section 3.03 Least Common Denominators".  These are my own explanations that are written especially for students who have trouble with math!  


In addition, many of my exercises are solved in my "Math in Living Color" pages that accompany each of these sections.


I hope you like my curriculum .  I have other topics as well.  When I was teaching, my own students were unanimous that my explanations were a LOT easier to understand than the traditional textbooks.  If you like it, please recommend it to your family and friends who need help with math!!  Like algebra.com, it's all FREE!!


Dr. Robert J. Rapalje, Retired
Seminole State College of Florida
Altamonte Springs Campus