C is for Cookie:

Ten identical cookies are to be distributed among 5 different 
kids (A, B, C, D, and E). All ten cookies are distributed. How 
many different ways can the five kids be given cookies? HINT: 
you could keep track of all the different combinations: first 
assume A gets 10, then A gets 9, then .... but there is a faster 
way of doing it, that allows one to solve it in one's head, 
without paper, without pens! (standard problem)