Common Denominator
Fractions have the same number at the bottom
5/
6
3/
6
4/
6
These all have the same common denominator
http://www.mathsisfun.com/numbers/common-denominator.html
Least Common Denominator
http://www.mathsisfun.com/least-common-denominator.html
http://www.youtube.com/watch?v=KPZnoF0V9ZI