In discrete math, in combinatorics, there is a problem that often confuses me. Supposedly there is a way to solve this problem.
How many ways can we fit 30 marbles in 7 boxes? Supposedly this is a problem that has a solution of the form, n + r - 1 choose r. Where r is the marbles in this case, and n is the boxes.
Can you offer an explanation for this, specifically a one that is more intuitive, since I have been struggling with grasping this concept.