probability question help (1 Viewer)

[Benmc]

how do you do this question.
7 people are to be seated at a round table. two people, kev and jill, refuse to sit next to each other. how many seating arrangements are then possible?

 

[rama_v]

No restrictions = 6!
But two cant sit together
so its 6! - the times they do sit together
= 6! - (5!x2!)
= 6! - (240)
= 480

I think, this is my worst topic

 

[word.]

find the number arrangements of them together
you do this by treating them as one group
so there are '6' people around the table
number of arrangements around the table = 5!;
within the 2 people = 2!,
5! * 2!

minus the total arrangements
6! - 5!*2!

 

[Condog]

i believe this is how its done:
there are 6! ways the people can sit around the table
there are 5! ways in which two people can be seated together but they can be either side of each other so its 2(5!) (u take the 2 people as one person)
tthen the number of arrangements which the two people cannot be together is
6!-2(5!)

 

[Benmc]

No restrictions = 6!
But two cant sit together
so its 6! - the times they do sit together
= 6! - (5!x2! / 5)
= 6! - (48)
= 672

I think, this is my worst topic

nah the answer is 480

 

[rama_v]

Yeah, I edited it just then lol,
I divided by 5 for no apparent reason
shows how much i know about permutations

 

[jake2.0]

well actually its a combination

 

[Dumsum]

well actually its a combination

I'm pretty sure this is a permutation.



Who else thinks that Kev and Jill will end up hooking up in the future? Lol. These math problems are always all about people hating each other

 

[Stefano]

i believe this is how its done:
there are 6! ways the people can sit around the table
there are 5! ways in which two people can be seated together but they can be either side of each other so its 2(5!) (u take the 2 people as one person)
tthen the number of arrangements which the two people cannot be together is
6!-2(5!)

Exactly correct.


Benmc - just remember that the amount of ways the two peope CANNOT sit together is the total way of seating everyone minus the amount of ways those two people can sit together.