Thread: Circular Permutation??

if there are 7 boys and 5 girls, how many circular arrangements are possible if the ladies do not sit adjacent to each other.??

Seat the boys at the table.
That can be done in $\displaystyle 6!$ ways. WHY?
That creates seven places to place five chairs.
So what do you think the answer is?

Originally Posted by Plato

Seat the boys at the table.
That can be done in $\displaystyle 6!$ ways. WHY?
That creates seven places to place five chairs.
So what do you think the answer is?

i think:-

=6!*p(7,5)
=6!*7!/(7-5)!

???

Well if I were to confirm that answer, I would have no way to know what you understand about this question.

Tell us what those numbers mean!

Originally Posted by Plato

Well if I were to confirm that answer, I would have no way to know what you understand about this question.

Tell us what those numbers mean!

as per your suggestion;-
boys ways;-(7-1)=6!
now there are 5 girls and 7 seats(in b/w boys) so there are P(7,5) number of ways, the girls can sit.
p(7,5)=7!/(7-5)!

i.e, total no. of ways= 6!*p(7,5)
= 6!*7!/(7-5)!
= 1814400 (but this ans is wrong).
ans is = 252

Originally Posted by Plato

That answer is completely wrong!
You need to contact your educational authority.
That is incompetent!

ans=252 is in my book.
what should i do if i m doing any thing wrong with girls ways???
and what should be the ans.??

Is it more than a coincidence that $\displaystyle \frac{15120}{60} = 252$?

Maybe the author just miscalculated and divided by 60 somehow

"Sorry guys, I'll fix that in Dinner Party Combinatorics V2.0"