How many ways are there to put 4 balls in 3 boxes if the balls are distinguishable but the boxes are not?
The cases are {4,0,0}, {3,1,0}, {2,1,1}, {2,2,0}
Counting the number of ways in each case gives us an answer of 1 + 4 + 6 + 6 = 17.
sherwyo:
Thanks for telling the forum the answer but
next time how about saying thanks to your answer for their time and effort as well.
Guest answerer:
The reason you are out by 3 is your 2,2,0 case
You said 4C2 which was right but what is left behind is also a pile of 2.
Once you have chosen one pile of 2 you have also chose its compliment. So you have to divide by 2
6/2=3
That is why your answer was 3 too big.