In how many ways can 4 balls be placed in 4 boxes if 3 balls are indistinguishably white, 1 ball is black, and the boxes are indistinguishable?
There are 4 ways to choose the box for the black ball.
After we have placed the black ball, there are 3! ways to arrange the white balls in the remaining 3 boxes.
So the total number of ways to place the balls is 4 * 3! = 24.
