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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## From a group of J employees, K will be selected, at random, tagged by: swerve ##### This topic has 2 member replies ### Top Member ## From a group of J employees, K will be selected, at random, ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult From a group of J employees, K will be selected, at random, to sit in a line of K chairs. There are absolutely no restrictions, either in the selection process nor in the order of seating - both are entirely random. What is the probability that the employee Lisa is seated exactly next to employee Phillip? 1) K = 15 2) K = J The OA is C Source: Magoosh ### Top Member Junior | Next Rank: 30 Posts Joined 07 Oct 2017 Posted: 22 messages From a group of J employees, K will be selected, at random, to sit in a line of K chairs. There are absolutely no restrictions, either in the selection process nor in the order of seating - both are entirely random. What is the probability that the employee Lisa is seated exactly next to employee Phillip? We need both K, J values in order to find the probability 1) K = 15 Still J is not given Insufficient 2) K = J We can group Lisa and Phillip together and consider them as a single person, then we can arrange them in (K-1)!*2 But K value is unknown Insufficient 1 and 2 together, (K-1)!*2 = 14!*2 Sufficient Option C is correct ### Top Member Legendary Member Joined 02 Mar 2018 Posted: 777 messages Followed by: 1 members Statement 1 K=15 From J; 15 people are randomly selected to seat into 15 chairs but we don't know the exact value of of J. If J is much larger than 15, then it is likely that Lisa and Philip are not among the 15 employees that were randomly selected to seat in 15 Chairs, the two of them would have to be selected before we find out if they are actually sitted exactly next to to each other without knowing the value of J. Statement 1 is INSUFFICIENT. Statement 2 K=J If K=J then all employees are selected and seated If K=J is a smaller number like 4 or 3 :it is very certain that Lisa and Philip will be more likely to seat next to each other but if (K=J) is a Larger number like 100, then it is more likely that Lisa and Philip are seated far away from each other, without knowing the value of either J or K : statement 2 is clearly INSUFFICIENT. combining 2 statement together k = 15 and K=J hence (K=J=15) All 15 employees are seated combining the two employees, we can arrange 14 people in 14 seats $$\Pr obability\ that\ Lisa\ and\ Philip\ seat\ together\ =\frac{14!}{15!}$$ $$=\frac{14\cdot13\cdot12\cdot11\cdot10\cdot9\cdot8\cdot7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1}{15\cdot14\cdot13\cdot12\cdot11\cdot10\cdot9\cdot8\cdot7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1}$$ $$\frac{87178291200}{1307674368000}=\frac{1}{15}$$ $$\Pr obability\ that\ Lisa\ and\ Philip\ seat\ together=1-\frac{1}{15}=\frac{14}{15}$$ $$both\ statements\ together\ is\ SUFFICIENT\$$ $$answer\ is\ Option\ C$$ • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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