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

It is currently 20 Aug 2014, 18:26

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

An amphitheater has 50 rows of seats with 30 seats in the

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
VP
VP
User avatar
Joined: 14 May 2006
Posts: 1419
Followers: 4

Kudos [?]: 41 [0], given: 0

GMAT Tests User
An amphitheater has 50 rows of seats with 30 seats in the [#permalink] New post 11 Aug 2006, 14:01
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
An amphitheater has 50 rows of seats with 30 seats in the first row, 32 in the second, 34 in the third, and so on. Find the total number of seats for all U2 fans for the upcoming U2 concert. :wink: (make sure to count u2lover in the 1st row :lol: )
Senior Manager
Senior Manager
User avatar
Joined: 07 Jul 2005
Posts: 406
Location: Sunnyvale, CA
Followers: 2

Kudos [?]: 2 [0], given: 0

GMAT Tests User
Re: PS: Amphitheater [#permalink] New post 11 Aug 2006, 14:15
u2lover wrote:
An amphitheater has 50 rows of seats with 30 seats in the first row, 32 in the second, 34 in the third, and so on. Find the total number of seats for all U2 fans for the upcoming U2 concert. :wink: (make sure to count u2lover in the 1st row :lol: )


This is an A.P. series
Sum of n terms = n/2(2a + (n-1)d)
= 50/2(2*30 + 49*2)
= 50*79
=3950
VP
VP
User avatar
Joined: 14 May 2006
Posts: 1419
Followers: 4

Kudos [?]: 41 [0], given: 0

GMAT Tests User
Re: PS: Amphitheater [#permalink] New post 11 Aug 2006, 14:26
sgrover wrote:
u2lover wrote:
An amphitheater has 50 rows of seats with 30 seats in the first row, 32 in the second, 34 in the third, and so on. Find the total number of seats for all U2 fans for the upcoming U2 concert. :wink: (make sure to count u2lover in the 1st row :lol: )


This is an A.P. series
Sum of n terms = n/2(2a + (n-1)d)
= 50/2(2*30 + 49*2)
= 50*79
=3950


:shock: what's d? and what's A.P. series? is the latter Arithm. progression?
Senior Manager
Senior Manager
User avatar
Joined: 07 Jul 2005
Posts: 406
Location: Sunnyvale, CA
Followers: 2

Kudos [?]: 2 [0], given: 0

GMAT Tests User
Re: PS: Amphitheater [#permalink] New post 11 Aug 2006, 14:44
u2lover wrote:
sgrover wrote:
u2lover wrote:
An amphitheater has 50 rows of seats with 30 seats in the first row, 32 in the second, 34 in the third, and so on. Find the total number of seats for all U2 fans for the upcoming U2 concert. :wink: (make sure to count u2lover in the 1st row :lol: )


This is an A.P. series
Sum of n terms = n/2(2a + (n-1)d)
= 50/2(2*30 + 49*2)
= 50*79
=3950


:shock: what's d? and what's A.P. series? is the latter Arithm. progression?


Yes. A.P. is the arithmetic progression
a - first term
n - #terms
d - difference between any two consecutive terms.

If first term is a, then nth term is: a + (n-1)d
Sum of n terms = n/2(2a + (n-1)d)

It can be easily derived.
(a1 + a2 .. + an)/n = mean
a1 + a2 .. +an = mean*n

In any A.P. mean of n terms = mean of first and last
mean = (a + a + (n-1)d)/2
= (2a+(n-1)d)/2

subsituting,
sum = n/2(2a+(n-1)d)
Current Student
avatar
Joined: 28 Dec 2004
Posts: 3405
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 13

Kudos [?]: 158 [0], given: 2

GMAT Tests User
 [#permalink] New post 11 Aug 2006, 15:02
I am not sure if you can apply the progressive series here...

for instance say...

first row 30 seats
second row 32 seats
third row has 34 seats
well now if fourth row had 36 seats..Yes you can apply the progression series formula...

however if the 4th row had 38 seats..then you cant apply the progressive series...
VP
VP
User avatar
Joined: 29 Dec 2005
Posts: 1351
Followers: 6

Kudos [?]: 28 [0], given: 0

GMAT Tests User
Re: PS: Amphitheater [#permalink] New post 11 Aug 2006, 15:20
u2lover wrote:
An amphitheater has 50 rows of seats with 30 seats in the first row, 32 in the second, 34 in the third, and so on. Find the total number of seats for all U2 fans for the upcoming U2 concert. :wink: (make sure to count u2lover in the 1st row :lol: )


first row = 30
.
.
.
.
.
last row = 2 (50 - 1) + 30 = 128

so total = (50) (128 + 30)/(2) = 3950
Re: PS: Amphitheater   [#permalink] 11 Aug 2006, 15:20
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic The seating chart of an airplane shows 30 rows of seats eybrj2 7 24 Feb 2012, 22:09
7 Theater M has 25 rows with 27 seats in each row. How many of quantum 8 20 Jun 2008, 01:27
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

An amphitheater has 50 rows of seats with 30 seats in the

  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®.