In combinatorics, stars and bars is a graphical aid for deriving certain combinatorial theorems. It can be used to solve a variety of counting problems, such as how many ways there are to put n indistinguishable balls into k distinguishable bins. The solution to this particular problem is given by the binomial coefficient , which is the number of subsets of size k − 1 that can be formed from a set of size n + k − 1.