Find all School-related info fast with the new School-Specific MBA Forum

It is currently 30 May 2015, 05:19

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Theater M has 25 rows with 27 seats in each row. How many of

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 14 May 2008
Posts: 71
Followers: 1

Kudos [?]: 36 [0], given: 0

Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 20 Jun 2008, 01:27
2
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

60% (01:45) correct 40% (01:04) wrong based on 144 sessions
Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied during a certain show?

(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats
per row for the front 20 rows.

(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats
per row for the back 15 rows.

Hope you like that one! :)
[Reveal] Spoiler: OA
1 KUDOS received
SVP
SVP
avatar
Joined: 04 May 2006
Posts: 1936
Schools: CBS, Kellogg
Followers: 19

Kudos [?]: 458 [1] , given: 1

Premium Member
Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 20 Jun 2008, 01:38
1
This post received
KUDOS
quantum wrote:
Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied
during a certain show?
(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats
per row for the front 20 rows.
(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats
per row for the back 15 rows.

Hope you like that one! :)


1 not suff, because you have info. only about the front 20 rows, the back 5 rows, you dont know whether it is occupied?

2. the same about 10 front rows.

I think E
_________________

GMAT Club Premium Membership - big benefits and savings

Manager
Manager
User avatar
Joined: 24 Apr 2008
Posts: 162
Followers: 1

Kudos [?]: 39 [0], given: 0

Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 20 Jun 2008, 01:49
Yes C cannot be the case - mathematically: Let 0-10 be o1 and v1 for occupied & Vacant respectively similary for 10-20 o2 & v2 and the 20-25 as o3 & v3

From Q stem: o1+v1=270, o2+v2=270 & o3+v3=135
Target: To find o1+o2+o3

Now frm st 1: v1+v2=200 -------insuffi

St2: v2+v3=300 ---Insuffi

St1+2: We end up with eqs: o1+o2=270 & o2+o3=105 ---- no way can we find the target hence E.
SVP
SVP
avatar
Joined: 04 May 2006
Posts: 1936
Schools: CBS, Kellogg
Followers: 19

Kudos [?]: 458 [0], given: 1

Premium Member
Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 20 Jun 2008, 02:03
quantum wrote:
But can someone explain in details why C is wrong?


Oh, just think that you can figure out! :lol:

C is combine 1 and 2. You see the intersection between group1(statement1) and group2(statement2) has NOT-fixed number of seats unoccupied. You can be sure only that the number of rows in the intersection is 5 rows, but statement1 say average per row is 10 unoccupied and statement2 says everage per row is 20 unoccupied. So the total number of seats unoccupied in 5 rows in the intersection can be 50 or 100 seats.

E
_________________

GMAT Club Premium Membership - big benefits and savings

8 KUDOS received
Manager
Manager
User avatar
Joined: 11 Apr 2008
Posts: 129
Location: Chicago
Followers: 1

Kudos [?]: 39 [8] , given: 0

Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 20 Jun 2008, 13:02
8
This post received
KUDOS
1
This post was
BOOKMARKED
quantum wrote:
Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied
during a certain show?
(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats
per row for the front 20 rows.
(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats
per row for the back 15 rows.

Hope you like that one! :)


E
Attachments

theater.gif
theater.gif [ 9.82 KiB | Viewed 7156 times ]


_________________

Factorials were someone's attempt to make math look exciting!!!

Manager
Manager
avatar
Joined: 16 Jan 2007
Posts: 73
Followers: 1

Kudos [?]: 9 [0], given: 0

Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 21 Jun 2008, 01:17
quantum wrote:
Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied
during a certain show?
(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats
per row for the front 20 rows.
(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats
per row for the back 15 rows.

Hope you like that one! :)


Stem :- Total number is seats = 25 * 27 = 675
To find :- No of seats occupied 'x'.

Option1 ) Avg of 10 unoccupied seats in the front row
Number of seats unocupied in the front 20 rows = 200 seats.
Total number of occupied seats = 675 -200 = 475 .
SUFF

Option 2 ) Avg of 10 unoccupied seats in the back 15 rows:- 20
Total number of seats unoccupied = 20 *15 = 300
Total number of occupied seats = 675 -300 = 375 .
SUFF

IMO = D
Manager
Manager
avatar
Joined: 22 Jul 2009
Posts: 205
Location: Manchester UK
Followers: 2

Kudos [?]: 89 [0], given: 6

Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 08 Jan 2010, 13:23
1
This post was
BOOKMARKED
Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied during a certain show?

(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats per row for the front 20 rows.
(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats per row for the back 15 rows.
Manager
Manager
avatar
Joined: 06 Jan 2010
Posts: 73
Followers: 2

Kudos [?]: 9 [0], given: 15

Re: Theater M [#permalink] New post 10 Jan 2010, 09:09
we know that there were 17*20 people in the first 20 rows

and

7*15 people in the last 15 rows


however there is an overlap of 10 rows between the first 20 and the last 15 rows.

to know how many people occupied those 10 rows, additional information is needed.

hence answer is E

a venn diagram will help in this question
1 KUDOS received
VP
VP
User avatar
Status: Far, far away!
Joined: 02 Sep 2012
Posts: 1125
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8
Followers: 142

Kudos [?]: 1380 [1] , given: 219

GMAT ToolKit User
Re: Theater M has 25 rows with 27 seats in each row. [#permalink] New post 26 Apr 2013, 21:53
1
This post received
KUDOS
Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied during a certain show?

(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats per row for the front 20 rows.
Clearly not sufficient, no info about other rows

(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats per row for the back 15 rows.
Clearly not sufficient, no info about other rows

1+2)With 1 we know that there are 200 unoccupied in the first 20 rows, with 2 we know that there are 300 unoccupied in the last 15 rows.
Because we don't know how many seats there are in the common part (rows 10-20) both statements are still not sufficient.
E

Hope it's clear, let me know
_________________

It is beyond a doubt that all our knowledge that begins with experience.

Kant , Critique of Pure Reason

Tips and tricks: Inequalities , Mixture | Review: MGMAT workshop
Strategy: SmartGMAT v1.0 | Questions: Verbal challenge SC I-II- CR New SC set out !! , My Quant

Rules for Posting in the Verbal Forum - Rules for Posting in the Quant Forum[/size][/color][/b]

SVP
SVP
User avatar
Joined: 06 Sep 2013
Posts: 2046
Concentration: Finance
GMAT 1: 770 Q0 V
Followers: 26

Kudos [?]: 303 [0], given: 354

GMAT ToolKit User
Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 11 Oct 2013, 05:32
sagarsabnis wrote:
Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied
during a certain show?

(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats
per row for the front 20 rows.
(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats
per row for the back 15 rows.
[Reveal] Spoiler:
E


Let me try to explain this one.

So we are asked how many seats occupied.

Statement 1 - Clearly insfficient, we only have information about 20 rows
Statement 2- Same here, we are missing information on other rows

Now both (1) and (2) together -
So we have from the 1st statement that the total number of seats for the first 20 rows that were unnocupied totaled 200.
And also the unnocpied for the back 15 rows were 300.
But we have an overlap here between rows. If we don't have more information it will be impossible to know. Imagine a venn diagram and visualize the intersection between both. As long as you don't have the exact value for the intersection it will be impossible to know the total number of unnocupied seats and hence know what the occupied seats are.

I think this will do for now.
Hope it helps
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 4977
Followers: 300

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

Premium Member
Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 22 Nov 2014, 21:50
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

1 KUDOS received
Intern
Intern
avatar
Joined: 26 Mar 2013
Posts: 23
Location: India
Concentration: Finance, Strategy
Followers: 0

Kudos [?]: 8 [1] , given: 2

Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 17 Jan 2015, 12:09
1
This post received
KUDOS
E

Try seeing extremes.... statements didnt concretize the seating pattern so

divide rows into 3 parts first 10 + 10 + 5 rows

extreme 1: Middle set takes average of say 30 (higher side)

first 10 has average of <10 unoccupied (say 5..u can calculate actual possibility) + next 10 say abt 30 + last 5 has average of <20 unoccupied => would have a overall count on lower side

extreme 2: Middle set takes average of say 5

first 10 has average of >10 unoccupied (say 20..u can calculate actual possibility) + next 10 say abt 5 + last 5 has average of >20 unoccupied => would have a overall count on higher side

The logic is the middle set can act as cushion so we have a range of possibilities

Had their been no overlap....then we can find the total

Hope it helps..!
2 KUDOS received
Intern
Intern
avatar
Joined: 26 Mar 2013
Posts: 23
Location: India
Concentration: Finance, Strategy
Followers: 0

Kudos [?]: 8 [2] , given: 2

Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 17 Jan 2015, 12:09
2
This post received
KUDOS
E

Try seeing extremes.... statements didnt concretize the seating pattern so

divide rows into 3 parts first 10 + 10 + 5 rows

extreme 1: Middle set takes average of say 30 (higher side)

first 10 has average of <10 unoccupied (say 5..u can calculate actual possibility) + next 10 say abt 30 + last 5 has average of <20 unoccupied => would have a overall count on lower side

extreme 2: Middle set takes average of say 5

first 10 has average of >10 unoccupied (say 20..u can calculate actual possibility) + next 10 say abt 5 + last 5 has average of >20 unoccupied => would have a overall count on higher side

The logic is the middle set can act as cushion so we have a range of possibilities

Had their been no overlap....then we can find the total

Hope it helps..!
Manager
Manager
avatar
Joined: 23 Sep 2013
Posts: 68
Concentration: Strategy, Marketing
WE: Programming (Computer Software)
Followers: 0

Kudos [?]: 19 [0], given: 13

Reviews Badge CAT Tests
Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 10 Mar 2015, 03:58
Bunuel ..Karishma and other experts !

Is there a faster and a more logical way to solve this problem (or similar type of problems)?

Regards,
SR
Expert Post
EMPOWERgmat Instructor
User avatar
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 2240
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Followers: 95

Kudos [?]: 605 [0], given: 43

Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 10 Mar 2015, 20:30
Expert's post
Hi solitaryreaper,

The type of situation that this DS question is based on is relatively rare, but the most efficient way to deal with it is to think about the "extreme" possibilities in the numbers.

I assume that you recognized that each Fact was insufficient on its own (since neither Fact gives you enough information about ALL 25 rows. When combining Facts, you have to recognize that there's an "overlap" - the "front 20 rows" mentioned in Fact 1 and the "back 15 rows" mentioned in Fact 2 include a series of 10 rows that are a part of BOTH calculations (remember that there are only 25 rows in TOTAL).

It's in those 10 overlapping rows that you can greatly impact the calculations. What if ALL of those seats were full? What if ALL of those seats were empty? In those two examples, you will find 2 different answers to the question. If you've comfortable drawing pictures and 'visualizing' the calculations, you can actually avoid most of the 'math' altogether.

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

Rich Cohen
Rich.C@empowergmat.com
http://www.empowergmat.com

EMPOWERgmat GMAT Club Page, Study Plans, & Discounts
http://gmatclub.com/blog/courses/empowergmat-discount/?fl=menu

Image

Manager
Manager
avatar
Joined: 23 Sep 2013
Posts: 68
Concentration: Strategy, Marketing
WE: Programming (Computer Software)
Followers: 0

Kudos [?]: 19 [0], given: 13

Reviews Badge CAT Tests
Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 16 Mar 2015, 23:38
EMPOWERgmatRichC wrote:
Hi solitaryreaper,

The type of situation that this DS question is based on is relatively rare, but the most efficient way to deal with it is to think about the "extreme" possibilities in the numbers.

I assume that you recognized that each Fact was insufficient on its own (since neither Fact gives you enough information about ALL 25 rows. When combining Facts, you have to recognize that there's an "overlap" - the "front 20 rows" mentioned in Fact 1 and the "back 15 rows" mentioned in Fact 2 include a series of 10 rows that are a part of BOTH calculations (remember that there are only 25 rows in TOTAL).

It's in those 10 overlapping rows that you can greatly impact the calculations. What if ALL of those seats were full? What if ALL of those seats were empty? In those two examples, you will find 2 different answers to the question. If you've comfortable drawing pictures and 'visualizing' the calculations, you can actually avoid most of the 'math' altogether.

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



Thanks Rich, that helps!

I was looking for a logical approach to tackle such problems under 2 minutes. I think it's not always fruitful to approach such problems in pure mathematical way(because one might end up loosing precious time and energy) . That's where GMAT surprise you by throwing such problems that demand for a more logical approach.
IMO such problems and methodologies should be discussed in a greater number !

Regards,
Arun
Expert Post
EMPOWERgmat Instructor
User avatar
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 2240
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Followers: 95

Kudos [?]: 605 [0], given: 43

Re: Theater M has 25 rows with 27 seats in each row. How many of [#permalink] New post 18 Mar 2015, 10:40
Expert's post
Hi Arun,

You've hit on an important point - knowing MORE than one way to approach questions can be quite helpful on Test Day. For most of your life, you were taught just 1 way to approach a question. When you took a test in school, you were supposed to use that 1 way and so you studied just that 1 way. On the GMAT though, many questions are designed to 'reward' a Test Taker for being is a critical thinker or pattern-matcher more than for being a mathematician. During your studies, it's important to practice more than one approach so that you have the flexibility on Test Day to decide which method is easiest/fastest.

Another thing worth noting is that you should NOT be trying to answer every Quant question within 2 minutes. The AVERAGE amount of time that you'll spend per question over the course of the entire Quant section is about 2 minutes, but your GOAL is actually to work in an efficient fashion. A question might require 1 minute or 3 minutes - and that's fine as long as you're not wasting time. If this question takes you 2.5 minutes, then that's not a problem.

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

Rich Cohen
Rich.C@empowergmat.com
http://www.empowergmat.com

EMPOWERgmat GMAT Club Page, Study Plans, & Discounts
http://gmatclub.com/blog/courses/empowergmat-discount/?fl=menu

Image

Re: Theater M has 25 rows with 27 seats in each row. How many of   [#permalink] 18 Mar 2015, 10:40
    Similar topics Author Replies Last post
Similar
Topics:
Theater M has 25 rows with 27 seats in each row. How many of gorden 1 11 Nov 2008, 15:24
Theater M has 25 rows with 27 seats in each row. How many of quantum 0 22 Nov 2014, 21:50
Theater M has 25 rows with 27 seats in each row. How many of goalsnr 2 01 Jun 2008, 12:50
Theater M has 25 rows with 27 seats in each row. How many of gluon 4 14 Sep 2007, 11:46
Theater M has 25 rows with 27 seats in each row. How many of ricokevin 4 02 Apr 2007, 05:21
Display posts from previous: Sort by

Theater M has 25 rows with 27 seats in each row. How many of

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.