I've been really stuck on this problem. My current thinking is to first place the blue balls, then try and distribute the green balls across the boxes without restrictions? Any help would be greatly appreciated!
Problem: 6 numbered green balls and 2 indistinguishable blue balls are to be placed in five labelled boxes.
Restrictions
- each box contains at most one blue ball
- none of the boxes are left empty
Find the number of placements?