Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Derangement/Principle of Inclusion-Exclusion Question
Replies: 2   Last Post: Dec 11, 2009 2:38 AM

 Messages: [ Previous | Next ]
 naslund19 Posts: 1 Registered: 9/22/09
Derangement/Principle of Inclusion-Exclusion Question
Posted: Sep 22, 2009 2:51 PM

Hi, I was wondering if anyone could help me get started with this question:

6 groups of students each consisting of 9 students are in a theatre and sit in rows 1 to 6 and columns A to I, with all students in the same group sitting in the same row. All the students leave and come back, again sitting in rows 1 to 6 and columns A to I, all students in the same group are still sitting in the same row.

What is the probability that:

1. No group of students sits in its original row?
2. Exactly 2 groups of students sit in their original row?
3. At least 3 groups of students sit in their original row?
4. No students sit in their original row and no student sits in their original column?

Can anyone help me get started with this question, using the Principle of Inclusion-Exclusion?

Thanks!

Date Subject Author
9/22/09 naslund19
9/22/09 Ben Brink
12/11/09 jane