• NEW! FREE Beat The GMAT Quizzes
Hundreds of Questions Highly Detailed Reporting Expert Explanations
• 7 CATs FREE!
If you earn 100 Forum Points

Engage in the Beat The GMAT forums to earn
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 ## There are k-2 members in a certain band, including Jim... tagged by: swerve ##### This topic has 1 expert reply and 1 member reply ### Top Member ## There are k-2 members in a certain band, including Jim... There are k-2 members in a certain band, including Jim and Allan. Two members are to be selected to attend the Grammy awards ceremony. If there are 10 possible combinations in which Jim and Allan are not selected, what is the value of k? A. 5 B. 9 C. 15 D. 18 E. 25 The OA is B. Please, can any expert explain this PS question for me? I tried to solve it but I can't get the correct answer. I need your help. Thanks. ### Top Member Master | Next Rank: 500 Posts Joined 15 Oct 2009 Posted: 330 messages Upvotes: 27 swerve wrote: There are k-2 members in a certain band, including Jim and Allan. Two members are to be selected to attend the Grammy awards ceremony. If there are 10 possible combinations in which Jim and Allan are not selected, what is the value of k? A. 5 B. 9 C. 15 D. 18 E. 25 The OA is B. Please, can any expert explain this PS question for me? I tried to solve it but I can't get the correct answer. I need your help. Thanks. If you find the combination formula confusing in this context, try using slots. There are two slots available. Since you want to pick from the group excluding Jim and Allan, there are K-4 members to choose from. Number of choices to fill the first slot is K-4. Therefore, the number of choices to fill the second slot is K-5. Therefore, there are (K-4)*(K-5) groups of two, BUT this treats a group AB and BA as separate groups, which they are not, so need to divide by 2. So, there are (K-4)*(K-5)/2 choices. The problem indicates that there are 10 combinations, therefore: (K-4)*(K-5)/2 = 10 > K^2 - 9K + 20 =20 K^2 = 9K, therefore K=9, B ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2950 messages Followed by: 19 members Upvotes: 43 swerve wrote: There are k-2 members in a certain band, including Jim and Allan. Two members are to be selected to attend the Grammy awards ceremony. If there are 10 possible combinations in which Jim and Allan are not selected, what is the value of k? A. 5 B. 9 C. 15 D. 18 E. 25 We are given that there are k - 2 members in a band, including Jim and Allan. We are also given that 2 members are selected to attend the Grammy awards, not including Jim or Allan. We need to determine the value of k. Since there are k - 2 members, if Jim and Allan are not selected, we have k - 2 - 2 = k - 4 members from which we can select. We can create the following equation to determine k: (k - 4)C2 = 10 (k - 4)!/[2!(k - 4 - 2)!] = 10 (k - 4)!/[2!(k - 6)!] = 10 (k - 4)(k - 5)(k - 6)!/[2!(k - 6)!] [(k - 4)(k - 5)]/2! = 10 k^2 - 9k + 20 = 20 k^2 - 9k = 0 k(k - 9) = 0 k = 0 or k = 9 Since k cannot be zero, k = 9. Answer: B _________________ Scott Woodbury-Stewart Founder and CEO scott@targettestprep.com See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE 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 • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

Available with Beat the GMAT members only code

• FREE GMAT Exam
Know how you'd score today for \$0

Available with Beat the GMAT members only code

• 5-Day Free Trial
5-day free, full-access trial TTP Quant

Available with Beat the GMAT members only code

### Top First Responders*

1 Ian Stewart 44 first replies
2 Brent@GMATPrepNow 34 first replies
3 Scott@TargetTestPrep 32 first replies
4 Jay@ManhattanReview 31 first replies
5 GMATGuruNY 18 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

### Most Active Experts

1 Scott@TargetTestPrep

Target Test Prep

139 posts
2 Max@Math Revolution

Math Revolution

90 posts
3 Ian Stewart

GMATiX Teacher

53 posts
4 Brent@GMATPrepNow

GMAT Prep Now Teacher

51 posts
5 Jay@ManhattanReview

Manhattan Review

31 posts
See More Top Beat The GMAT Experts