Thread: Permutations question...

In how many ways can 12 basketball players be assigned to six double rooms?

The answer is
12!
__
(2!)^6

But i dont understand why its done that way.

The number of rearragements of the string "AABBCC" is .
Because there are six letters, but three letters are repeat twice.
So we divide to account for that.
So think about a string "AABBCCDDEEFF". That is six rooms A-F, two to a room.
Then the team roster can correspond to any one of the arrangements of the 12-length string.
Compare your given answer with this.

Hello, Saibot!

In how many ways can 12 basketball players be assigned to six double rooms?

The answer is: .

But i don't understand why it's done that way.

We could simply line up the twelve players: .
. . There are: 12! permuations.

Then partition them in pairs: .

So that go to room #1 . . . go to room #2 . . . etc.

But among the possible permutations of the twelve players,
. . there is a lot of duplication.


With our game plan, another permuation would be: .

But this partitioning,
. . is identical to the first room assignment.
. . ( is in #1, is in #2, etc.)

So if a pair is reversed, it results in a duplicated room assignment.


How many reversals are there?
Each of the six pairs can be reversed or not-reversed.
So there are: . possible reversals (each creating a duplication).

To eliminate the duplications, we divide by


Therefore, the number of room assignments is: .


I hope all that is clear enough . . .

Thankks

very very gj

now i jsut have one moer question :'(