TEST 38 #10

Expert replies

dunkin77: Master | Next Rank: 500 Posts; Posts: 269; Joined: Sun Apr 01, 2007 5:41 am

by dunkin77 » Tue May 01, 2007 1:58 am

10. The president of a country and 4 other dignitaries are scheduled to sit in a row on the 5 chairs represented above. If the president must sit in the center chair, how many different seating arrangements are possible for the 5 people?
(A) 4
(B) 5
(C) 20
(D) 24
(E) 120

Hi,
I thought the answer was E) by doing 5P4 but the answer is D) ... Can you help?

Like this post

Source: Beat The GMAT — Problem Solving | Tue May 01, 2007 1:58 am

Cybermusings: Legendary Member; Posts: 559; Joined: Tue Mar 27, 2007 1:29 amFollowed by: 2 members; Thanked: 5 times

by Cybermusings » Tue May 01, 2007 8:54 am

Fix the president in the middle chair

Other 4 people can be arranged in 4*3*2*1 = 24 ways

Like this post

bww: Senior | Next Rank: 100 Posts; Posts: 55; Joined: Sun Apr 29, 2007 6:25 am; Location: MA; Thanked: 1 times

by bww » Wed May 02, 2007 5:36 pm

hey there...can someone help? so in the case above you used 4! or n!, right? isn't n! when you must choose from a set of n objects from the source to fill specific spots when order matters?

so when would you use n!/(n-r)! ?

thx!

Like this post

mschling52: Master | Next Rank: 500 Posts; Posts: 105; Joined: Mon Sep 18, 2006 12:34 pm; Location: OH; Thanked: 7 times; GMAT Score:780

by mschling52 » Thu May 03, 2007 5:06 am

I believe the permutation formula you refer to still holds in this case. We have four spots to fill and four people to fill them, so

nPr = n!/(n-r)!

4P4 = 4!/(4-4)! = 4!/0! = 4! = 24

since 0! is defined to be 1.

Like this post

ns88: Senior | Next Rank: 100 Posts; Posts: 33; Joined: Sat Apr 14, 2007 8:29 am

by ns88 » Sat May 05, 2007 10:25 am

Whenever there’s a question that involves that two people must sit together, or one person has to sit somewhere specifically, treat it as one person. Thus five becomes four factorial.

If all five people can sit anyway they want, then 5!

Like this post

GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8137; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Tue Dec 12, 2017 6:22 am

dunkin77 wrote:10. The president of a country and 4 other dignitaries are scheduled to sit in a row on the 5 chairs represented above. If the president must sit in the center chair, how many different seating arrangements are possible for the 5 people?
(A) 4
(B) 5
(C) 20
(D) 24
(E) 120

We are given that we must arrange 5 people in a row; however, the president MUST BE seated in the center chair. Since the president's seat is already determined, we need to arrange 4 people, which can be done in 4! = 24 ways.

Answer: D

Scott Woodbury-Stewart
Founder and CEO
[email protected]

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review