# Re: Inclusion-Exclusion Principle

*From*: "Proginoskes" <CCHeckman@xxxxxxxxx>*Date*: 3 Dec 2005 22:06:45 -0800

Little wrote:

> Could someone explain to me how to use the Inclusion-Exclusion

> Principle to solve this problem.

>

> Question: A carousel has eight seats, each seat is distinct. Eight

> girls are seated on the carousel facing forward ( each girl looks at

> another girl's back). In how many ways can they change seats so that

> each has a different girl in front of her? How can the problem change

> when the seats are identical?

>

> Thanks a lot for the help.

Google for "derangement".

--- Christopher Heckman

.

**References**:**Inclusion-Exclusion Principle***From:*Little

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