Rakibul Raju Posted May 4, 2014 Share Posted May 4, 2014 If ‘12’ persons are seated at a round table, what is the probability that two particulars persons sit together? Quote Link to comment Share on other sites More sharing options...
Chromepal Posted July 24, 2014 Share Posted July 24, 2014 12 persons can sit along around a table in (12-1)! ways i.e 11! Now considering that the 2 members who has to sit together as one unit, we have 11 units altogether, who can sit along in (11-1)! i.e 10! ways Also the 2 persons sitting together can exchange their positions in 2! ways So the probability is (10! * 2)/11! = 2/11 Quote Link to comment Share on other sites More sharing options...
Brent Hanneson Posted August 2, 2014 Share Posted August 2, 2014 If ‘12’ persons are seated at a round table, what is the probability that two particulars persons sit together? We don't need to apply any counting techniques if we look at it this way: What is the probability that Ann and Bea sit together. Let's just focus on Ann for a moment. What is the probability that Bea is sitting beside her? Well, there are 11 remaining seats and 2 of them are beside Ann. So, P( Ann and Bea sit together) = 2/11 Cheers, Brent Quote Link to comment Share on other sites More sharing options...
optimus141 Posted January 14, 2016 Share Posted January 14, 2016 We don't need to apply any counting techniques if we look at it this way: What is the probability that Ann and Bea sit together. Let's just focus on Ann for a moment. What is the probability that Bea is sitting beside her? Well, there are 11 remaining seats and 2 of them are beside Ann. So, P( Ann and Bea sit together) = 2/11 Cheers, Brent Why is it that the number of ways 12 people can be seated at a round table is 11!? Why not 12!? explain please? and also the rest of the proces please. Thanks Quote Link to comment Share on other sites More sharing options...
Brent Hanneson Posted January 21, 2016 Share Posted January 21, 2016 Why is it that the number of ways 12 people can be seated at a round table is 11!? Why not 12!? explain please? and also the rest of the proces please. Thanks You will notice that I never said that 12 people can be seated at a round table in 11! ways (Chromepal made this claim). I'm not a big fan of "people sitting at a circle" questions, because the assumption is that the seats are identical. Since this is not stated in the question, I solved it in a way that does not require us to make this assumption. Cheers, Brent Quote Link to comment Share on other sites More sharing options...
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