# Thread: Circular table permutations problem

1. ## Circular table permutations problem

Hey, i have problem understanding how to get result for circular permutations where i have repeating elements.
I have 10 people in circle, 3 man and 7 women. How can i get number of permutations?

Result in book is 36.
I tried
(9!/2!+7!)+(9!/3!+6!)=120 which is wrong.

2. ## Re: Circular table permutations problem

Originally Posted by PJani
Hey, i have problem understanding how to get result for circular permutations where i have repeating elements. I have 10 people in circle, 3 man and 7 women. How can i get number of permutations?

Result in book is 36.
That problem as you have posted it is absolutely incomplete.

As stated the answer is simply $\displaystyle 9!$.

There must be many more conditions placed on the groups of men and women.

Please add in those further conditions. That is the only way the answer $\displaystyle 36$ makes any sense.

3. ## Re: Circular table permutations problem

Heh sory, my mistake!
How can i get number of permutations where i distinguish persons only by gender?

4. ## Re: Circular table permutations problem

Originally Posted by PJani
Heh sory, my mistake!
How can i get number of permutations where i distinguish persons only by gender?
In the future, please try to be clear and complete.

Place a female anywhere at the table.
Now you have a string $\displaystyle ffmmmmmmm$ to arrange: $\displaystyle \frac{9!}{2!\cdot 7!}=?$ ways.

Start at the seated female's right and seat each of those strings counter-clockwise.

5. ## Re: Circular table permutations problem

Why do you start with females? And why is $\displaystyle \frac{9!}{2!\cdot 7!}=?$ and not $\displaystyle \frac{9!}{3!\cdot 6!}=?$