It is currently 23 Feb 2018, 04:13

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Seven children — A, B, C, D, E, F, and G — are going to sit in seven c

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
3 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43892
Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 04 Mar 2015, 03:36
3
This post received
KUDOS
Expert's post
16
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

69% (01:40) correct 31% (01:53) wrong based on 232 sessions

HideShow timer Statistics

Seven children — A, B, C, D, E, F, and G — are going to sit in seven chairs in a row. Children A & B must sit next to each other, and child C must be somewhere to the right of A & B. How many possible configurations are there for the children?

A. 600
B. 720
C. 1440
D. 4320
E. 4800



Kudos for a correct solution.
[Reveal] Spoiler: OA

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43892
Re: Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 04 Mar 2015, 03:38
Expert's post
1
This post was
BOOKMARKED
Bunuel wrote:
Seven children — A, B, C, D, E, F, and G — are going to sit in seven chairs in a row. Children A & B must sit next to each other, and child C must be somewhere to the right of A & B. How many possible configurations are there for the children?

A. 600
B. 720
C. 1440
D. 4320
E. 4800



Kudos for a correct solution.


Similar yet different questions:
six-children-a-b-c-d-e-and-f-are-going-to-sit-in-six-chairs-i-194098.html
seven-children-a-b-c-d-e-f-and-g-are-going-to-sit-in-seven-c-194097.html
seven-children-a-b-c-d-e-f-and-g-are-going-to-sit-in-seven-c-194096.html
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Expert Post
3 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43892
Re: Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 08 Mar 2015, 13:43
3
This post received
KUDOS
Expert's post
2
This post was
BOOKMARKED
Bunuel wrote:
Seven children — A, B, C, D, E, F, and G — are going to sit in seven chairs in a row. Children A & B must sit next to each other, and child C must be somewhere to the right of A & B. How many possible configurations are there for the children?

A. 600
B. 720
C. 1440
D. 4320
E. 4800



Kudos for a correct solution.


MAGOOSH OFFICIAL SOLUTION:

This problem is a notch harder than anything you are likely to see on the GMAT. If you can master the principles in this problem, you certainly will be able to handle almost any problem the GMAT could concoct.

First, consider the restriction of A & B. As with problem #1 above, there are 12 possibilities for A & B, counting both position and order.

Now, put the other five in any order — that’s 120 possibilities, for a total number of configurations of 1440. That number does not take into account the restriction with C.

Think about those 1440 configurations. In exactly half of them, C will be to the right of A & B, and exactly half, C will be to the left of A & B. Therefore, in (1/2)*1440 = 720 configurations, C will be to the right of A & B.

Answer = B
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

2 KUDOS received
Manager
Manager
avatar
B
Joined: 20 Aug 2015
Posts: 65
GMAT 1: 710 Q50 V36
GMAT ToolKit User
Re: Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 21 Oct 2015, 03:04
2
This post received
KUDOS
2
This post was
BOOKMARKED
A, B, C, D, E, F, G- seven children, of which A & B must sit next to each other. Considering them as one X (A, B), we have X, C, D, E, F, G. These can be arranged in 6! ways. But A,B can arrange themselves in 2! ways. So a total of 6!*2! ways = 1440. Since in exactly half of them, C will be to the right of A & B, and exactly half, C will be to the left of A & B, therefore 1440/2 = 720.

B is the right answer.
Director
Director
User avatar
G
Joined: 23 Jan 2013
Posts: 601
Schools: Cambridge'16
Re: Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 22 Oct 2015, 03:11
it is

(6!*2)/2=6!=720

B
Senior Manager
Senior Manager
User avatar
S
Joined: 24 Oct 2016
Posts: 317
Location: India
Concentration: Finance, International Business
Schools: IIMB
GMAT 1: 550 Q42 V28
GPA: 3.96
WE: Human Resources (Retail Banking)
Re: Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 08 Jul 2017, 04:58
the answer must be B
say AB*5*4*3*2*1=120
4*AB*4*3*2*1=96
4*3*AB*3*2*1=72
4*3*2*AB*2*1=48
4*3*2*1*AB*1=24
total = 360 ways now as we also know that AB can be rearranged in every case in 2 ways so 360*2=720 ways

if you liked it please press kudos
Intern
Intern
avatar
B
Joined: 14 Jun 2017
Posts: 11
GMAT ToolKit User Premium Member
Re: Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 21 Aug 2017, 22:00
Bunuel wrote:
Bunuel wrote:
Seven children — A, B, C, D, E, F, and G — are going to sit in seven chairs in a row. Children A & B must sit next to each other, and child C must be somewhere to the right of A & B. How many possible configurations are there for the children?

A. 600
B. 720
C. 1440
D. 4320
E. 4800



Kudos for a correct solution.


MAGOOSH OFFICIAL SOLUTION:

This problem is a notch harder than anything you are likely to see on the GMAT. If you can master the principles in this problem, you certainly will be able to handle almost any problem the GMAT could concoct.

First, consider the restriction of A & B. As with problem #1 above, there are 12 possibilities for A & B, counting both position and order.

Now, put the other five in any order — that’s 120 possibilities, for a total number of configurations of 1440. That number does not take into account the restriction with C.

Think about those 1440 configurations. In exactly half of them, C will be to the right of A & B, and exactly half, C will be to the left of A & B. Therefore, in (1/2)*1440 = 720 configurations, C will be to the right of A & B.

Answer = B



Hi, I am not quite sure i get how you come to the following conclusion "Think about those 1440 configurations. In exactly half of them, C will be to the right of A & B, and exactly half, C will be to the left of A & B"
Intern
Intern
avatar
B
Joined: 08 Jun 2015
Posts: 21
Location: United States
Concentration: Finance, Economics
WE: Engineering (Other)
Seven children — A, B, C, D, E, F, and G — are going to sit in seven c [#permalink]

Show Tags

New post 22 Aug 2017, 00:40
Hey Bunuel,
can you please check this approach.

Let 7 seats be 1 2 3 4 5 6 7

Condition : Children A & B must sit next to each other, and child C must be somewhere to the right of A & B.
So let this be the right side of A & B ----> 1 2 3 4 5 6 7.

Now considering A & B as a single unit, we have 6 seats for them. (Omitting the number 1 seat as if A & B starts sitting from seat number 1, C can't be seated to their right). So we have 6C2 X 2! = 30.

Since 3 out of 7 seats are filled as C, A, B needs to be seated in this particular order always. Out of remaining 4 seats 4 members can be arranged as 4! = 24.

Hence answer would be 24 X 30 = 720.
Seven children — A, B, C, D, E, F, and G — are going to sit in seven c   [#permalink] 22 Aug 2017, 00:40
Display posts from previous: Sort by

Seven children — A, B, C, D, E, F, and G — are going to sit in seven c

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.