It is currently 23 Nov 2017, 20:49

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

A group of 5 students bought movie tickets in one row next

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

Hide Tags

Current Student
User avatar
Joined: 21 Feb 2015
Posts: 10

Kudos [?]: 3 [0], given: 11

Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 21 Feb 2015, 23:26
"what is the probability that Bob and Lisa will each sit next to only one of the four other students from the group?"

Can someone please explain why the arrangement can't be " _ B _ L _ " or " _ L _ B _ "?
Does this not also satisfy that B & L also sit next to the other four students?

Kudos [?]: 3 [0], given: 11

Expert Post
1 KUDOS received
EMPOWERgmat Instructor
User avatar
P
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10178

Kudos [?]: 3536 [1], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 21 Feb 2015, 23:41
1
This post received
KUDOS
Expert's post
Hi icetray,

The prompt tells us that the 5 seats are in a row. For Bob/Lisa to sit next to JUST 1 student, they would both have to sit on the ENDS of the row. In the examples that you listed, Bob and Lisa are sitting next to 2 students, which does not fit the "restrictions" of what we're asked to deal with.

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3536 [1], given: 173

Intern
Intern
avatar
Joined: 13 Sep 2015
Posts: 7

Kudos [?]: 3 [0], given: 25

Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 28 Feb 2016, 23:46
A group of 5 students bought movie tickets in one row next to each other. If Bob and Lisa are in this group, what is the probability that Bob and Lisa will each sit next to only one of the four other students from the group?

(A) 5%
(B) 10%
(C) 15%
(D) 20%
(E) 25%


The most simplified version:

, Lisa and Bob have 2 plots to choose from 5 seats i.e, extremities. other 3 have 3! ways to choose seats and Bob and Lisa have 2! ways. Multiplying we get 3!*2!=12 ways. To find Lisa's and Bob's position Divide. total ways 5 people= 5!/3!*2! = 120/12= 10%. Hope this made sense.

Kudos [?]: 3 [0], given: 25

Current Student
User avatar
Joined: 03 May 2015
Posts: 262

Kudos [?]: 88 [0], given: 23

Location: South Africa
Concentration: International Business, Organizational Behavior
GPA: 3.49
WE: Web Development (Insurance)
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 19 Jul 2016, 23:40
mavery wrote:
I may be oversimplifying this, but isn't it just asking "what is the probability that Bob and Lisa are sitting on the outside of the group?"

1/5 * 1/4 = 1/20 = 5%

Disclaimer: I really suck at these problems, so I'm probably wrong.



Your approach is correct. But you forgot that there are 2 cases It could be B XXX L or L XXX B. So answer is your answer X 2
_________________

Kudos if I helped ;)

Kudos [?]: 88 [0], given: 23

Manager
Manager
avatar
B
Joined: 18 Jun 2016
Posts: 105

Kudos [?]: 21 [0], given: 76

Location: India
Concentration: Technology, Entrepreneurship
GMAT 1: 700 Q49 V36
WE: Business Development (Computer Software)
GMAT ToolKit User Reviews Badge
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 07 Sep 2016, 16:18
bkk145 wrote:
A group of 5 students bought movie tickets in one row next to each other. If Bob and Lisa are in this group, what is the probability that Bob and Lisa will each sit next to only one of the four other students from the group?

(A) 5%
(B) 10%
(C) 15%
(D) 20%
(E) 25%



So bob and lisa have to sit next to one another and cannot occupy corner seats
Seating arrangement :
x - - - X

this can be done in 3! * 2! ways

so probability would be 3! * 2! / 5! = 12 /120 = 1/10 = 10%

B is correct answer
_________________

If my post was helpful, feel free to give kudos!

Kudos [?]: 21 [0], given: 76

1 KUDOS received
Manager
Manager
avatar
B
Joined: 26 Jan 2016
Posts: 115

Kudos [?]: 24 [1], given: 55

Location: United States
GPA: 3.37
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 07 Sep 2016, 20:29
1
This post received
KUDOS
There are 2 different ways this can happen

LxxxB or BxxxL

Here is the probability of this happening (1/5)(3/4)(2/3)(1/2)(1/1)=2/20 or 1/10 10%

Kudos [?]: 24 [1], given: 55

Intern
Intern
avatar
B
Joined: 15 Aug 2012
Posts: 19

Kudos [?]: 4 [0], given: 44

Schools: AGSM '19
GMAT ToolKit User CAT Tests
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 16 Sep 2016, 18:11
joannaecohen wrote:
There are 2 different ways this can happen

LxxxB or BxxxL

Here is the probability of this happening (1/5)(3/4)(2/3)(1/2)(1/1)=2/20 or 1/10 10%


This is what I did too and was gonna reply until I saw this post. I'm glad my reasoning was right or we're both wrong :)

To explain again. Based on what the question asked, possibilities are BXXXL or LXXXB.

Probability of BXXXL happening:

B (1/5)*X(3/4)*X(2/3)*X(1/2)*L(1/1) = 1/20

Probability of LXXXB happening is also the same as above: 1/20

So probability of BXXXL OR LXXXB happening is 1/20+1/20=2/20=1/10=10%

Kudos [?]: 4 [0], given: 44

Manager
Manager
User avatar
B
Joined: 06 Oct 2015
Posts: 89

Kudos [?]: 16 [0], given: 49

Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 17 Oct 2016, 02:04
Hi all,
I have a problem with the question.
what is the probability that Bob and Lisa will each sit next to only one of the four other students.
Is the question saying that Bob and Lisa will sit at the extremes. However, I solve it treating subgroup like (B _ L) X X X and then solve for possible arrangement and got the same answer. But the official answer says that Bob and Lisa sat at the extremes. Is my understanding wrong?
Help me.
TIA

Kudos [?]: 16 [0], given: 49

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42338

Kudos [?]: 133161 [0], given: 12415

Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 17 Oct 2016, 03:14
NaeemHasan wrote:
Hi all,
I have a problem with the question.
what is the probability that Bob and Lisa will each sit next to only one of the four other students.
Is the question saying that Bob and Lisa will sit at the extremes. However, I solve it treating subgroup like (B _ L) X X X and then solve for possible arrangement and got the same answer. But the official answer says that Bob and Lisa sat at the extremes. Is my understanding wrong?
Help me.
TIA


The question asks about the probability that Bob and Lisa sit at the ends.

Check here: a-group-of-5-students-bought-movie-tickets-in-one-row-next-47450.html#p1265145
_________________

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

Kudos [?]: 133161 [0], given: 12415

Expert Post
EMPOWERgmat Instructor
User avatar
P
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10178

Kudos [?]: 3536 [0], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 17 Oct 2016, 14:04
NaeemHasan wrote:
Hi all,
I have a problem with the question.
what is the probability that Bob and Lisa will each sit next to only one of the four other students.
Is the question saying that Bob and Lisa will sit at the extremes. However, I solve it treating subgroup like (B _ L) X X X and then solve for possible arrangement and got the same answer. But the official answer says that Bob and Lisa sat at the extremes. Is my understanding wrong?
Help me.
TIA


Hi NaeemHasan,

In the example that you listed, Lisa is sitting next to TWO people - and that is not in line with what the question states.

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3536 [0], given: 173

Manager
Manager
avatar
B
Joined: 26 Jan 2016
Posts: 115

Kudos [?]: 24 [0], given: 55

Location: United States
GPA: 3.37
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 17 Oct 2016, 14:28
Probability that each will sit on the outside

1/5*3/4*2/3*1/2*1/1=1/20. This can happen two ways Bob is first Lisa is last, or Lisa is first and Bob is last. 1/20*2=2/20 or 10%

Kudos [?]: 24 [0], given: 55

Manager
Manager
User avatar
B
Joined: 06 Oct 2015
Posts: 89

Kudos [?]: 16 [0], given: 49

Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 19 Oct 2016, 02:23
EMPOWERgmatRichC wrote:
NaeemHasan wrote:
Hi all,
I have a problem with the question.
what is the probability that Bob and Lisa will each sit next to only one of the four other students.
Is the question saying that Bob and Lisa will sit at the extremes. However, I solve it treating subgroup like (B _ L) X X X and then solve for possible arrangement and got the same answer. But the official answer says that Bob and Lisa sat at the extremes. Is my understanding wrong?
Help me.
TIA


Hi NaeemHasan,

In the example that you listed, Lisa is sitting next to TWO people - and that is not in line with what the question states.

GMAT assassins aren't born, they're made,
Rich

Hi,
How? I allow only one person to sit between Bob and LIsa. Does this mean they sit next to two people? If so, Could you elaborate this, please.

Kudos [?]: 16 [0], given: 49

Expert Post
2 KUDOS received
EMPOWERgmat Instructor
User avatar
P
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10178

Kudos [?]: 3536 [2], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 19 Oct 2016, 20:57
2
This post received
KUDOS
Expert's post
Hi NaeemHasan,

In the example: B _ L _ _ _

Bob is sitting next to one person and Lisa is sitting next to two people.

The prompt asks for the probably that both Bob and Lisa will sit next to ONE person... NOT that Bob and Lisa will sit next to the SAME person. When sitting in a row of 6 people, the only way to sit next to just one person is to sit on the 'end' of the row. Thus, there are only two possible outcomes that meet this restriction:

B _ _ _ _ L
L _ _ _ _ B

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3536 [2], given: 173

Intern
Intern
avatar
B
Joined: 12 Nov 2009
Posts: 22

Kudos [?]: [0], given: 17

GMAT ToolKit User
Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 11 Nov 2017, 00:08
IMO:

There are total 5 seats in a row.
Bob and Lisa requires to sit in such a way that each one of them have only 1 person next to them.
Hence they can be seated only at the end of the row.
Now there are total 2 ways to sit for Bob and Lisa -either Bob on leftmost corner and Lisa on rightmost corner or vice versa

Now, this question is about probability, so we need to find- (Favorable cases) and ( Total cases).

Favorable cases=
1) B/L_ _ _ L/B

In between 3 vacant seats can be filled by remaining 3x2x1=6 ways.
Edge seats can be filled in 2 ways-Lisa on left -Bob on right or Lisa on right and Bob on left.
Hence Favorable cases= 6x2=12 ways

Total cases=
_ _ _ _ _

5 seats can be filled in 5 ! ways.
Hence Total cases= 5!

Hence probability of Bob or Lisa at the edge seats is=

Favorable/ Total= 12/5! x 100 = 10%

IMO B is the answer

Kudos [?]: [0], given: 17

Intern
Intern
avatar
B
Joined: 25 Mar 2017
Posts: 1

Kudos [?]: 0 [0], given: 1

Re: A group of 5 students bought movie tickets in one row next [#permalink]

Show Tags

New post 12 Nov 2017, 07:39
What I understand is that Bob and Lisa should have only person sitting next to them, this implies they take the edge seat
So total arrangement=5!=120
now the arrangement to meet the condition=3!2!( Arranging Bob and Lisa on edge seat=2!, Arranging the rest=3!)
So probability= 3!2!/5!=1/10=10%

Kudos [?]: 0 [0], given: 1

Re: A group of 5 students bought movie tickets in one row next   [#permalink] 12 Nov 2017, 07:39

Go to page   Previous    1   2   [ 35 posts ] 

Display posts from previous: Sort by

A group of 5 students bought movie tickets in one row next

  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®.