+137 How many ways are there to put 5 balls in 3 boxes if the balls are distinguishable but the boxes are not?
my logic: there are 5 balls and each ball can choose to go in each box or not ... so that is 3^5 which is 243. then divide by 3 to account for overcounting, which makes 81. apparently, this is the wrong solution. can someone please point me in the right direction? i will be quick to reply... thanks!!!
+2407 In this case, case work might just be easier.
Each number shows the number of balls in that box.
0 0 5 1 way
0 1 4 5 ways
0 2 3 10 ways
1 1 3 10 ways
1 2 2 15 ways
1+5+10+10+15 = 41
Hopefully it's 41. :))
=^._.^=
Edit: The more I think, the more unsure I hate this answer. There has to be a nicer way to solve this. Casework wasn't too bad since the numbers were small, but I don't like using it too often since calculation mistakes occur. I hope someone else also answers.
+129899 As long as we have no restrictions ( some boxes may be empty) the number of ways =
S ( 5 , 1) + S (5, 2) + S (5,3) = 1 + 15 + 25 = 41
Where "S" represents a Stirling number of the 2nd kind
+137 OMG
Thank you both for answering my question with such detailed solutions... i upvoted yourposts! :)
+771 nice problem. congrats on finding your solution! here is another i may present.
theres 243 arrangements to put 5 distinguishable balls in 3 distinguishable boxes. nice thinking with that, though :)
in these arrangements, theres one thats being counted three times - (5, 0, 0) i.e. put all the balls in one box. leaves us with 240.
for the other 240 cases, we divide by 3! instead of 3. thus, theres 240 / 6 = 40 cases. and 40 + 1 = 41. :)
