Hello everyone, I'm new to the forum and have an engineering problem I've been trying to solve for my job. The actual problem is rather hard to describe but it can best be explained with the following analogous scenario. Suppose I had a bag containing 3 red, 2 blue, and 1 green marbles. If I were to pull out 3 marbles only once from the bag; what are all the possible color combinations I could pull out? The answer is 6. RRR,RRB,RRG,RBB,RBG,BBG. In a simple combinations with repetitions problem the answer would be 10. RRR,RRB,RRG,RBB,RBG,RGG,BBB,BBG,BGG,GGG [(n+r-1)!]/[r!(n-1)!] However, because we have a defined population, the repetition is constrained by that population. I need to know the mathematical method for how to solve a problem of this type. In the real problem I'm trying to solve, the variables (ie. number drawn, number of colors, qty in bag) would be changing constantly so I'd like to set-up an excel spreadsheet "calculator" that would solve any problem of this type based off the inputs given. Any help that can be given would be greatly appreciated. Thanks.