(C) 2012-2013 David Liao (lookatphysics.com)
When we counted the number of ways to arrange objects in a row in the last video, we assumed that all the objects were distinct from each other. In this video, we relax this assumption and obtain the famous (L + N)! / (L! N!) formula for counting the number of ways to arrange L indistinguishable objects and N indistinguishable objects together in a row. This is also the formula for counting the number of combinations of L objects drawn from a container of L + N objects.