GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 18 Oct 2019, 19:07

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

If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find

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

Hide Tags

Find Similar Topics 
Manager
Manager
avatar
Joined: 19 Aug 2009
Posts: 77
If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find  [#permalink]

Show Tags

New post Updated on: 28 Sep 2012, 05:59
3
9
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

69% (02:32) correct 31% (02:54) wrong based on 222 sessions

HideShow timer Statistics

If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find value of n

A. 12
B. 13
C. 9
D. 10

Originally posted by virtualanimosity on 06 Nov 2009, 15:44.
Last edited by Bunuel on 28 Sep 2012, 05:59, edited 1 time in total.
Renamed the topic.
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58453
Re: Sequence2  [#permalink]

Show Tags

New post 06 Nov 2009, 16:22
2
3
General Discussion
SVP
SVP
User avatar
Joined: 29 Aug 2007
Posts: 1942
Re: Sequence2  [#permalink]

Show Tags

New post 07 Nov 2009, 23:53
virtualanimosity wrote:
Q.If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find value of n

1.12
2.13
3.9
4.10


Sum of 2+4+....+100 = 2(1+2+3+....+50) = 2(50x51/2) = 50x51

(50x51)/(1+3+5+....n terms) = 51/2
100 = 1+3+5+....n terms
100 = n (First term + last term)/2
100 = n (1 + 19)/2
n = 10
_________________
Verbal: http://gmatclub.com/forum/new-to-the-verbal-forum-please-read-this-first-77546.html
Math: http://gmatclub.com/forum/new-to-the-math-forum-please-read-this-first-77764.html
Gmat: http://gmatclub.com/forum/everything-you-need-to-prepare-for-the-gmat-revised-77983.html


GT
Current Student
User avatar
B
Joined: 03 Sep 2012
Posts: 372
Location: United States
Concentration: Healthcare, Strategy
GMAT 1: 730 Q48 V42
GPA: 3.88
WE: Medicine and Health (Health Care)
Re: Sequence2  [#permalink]

Show Tags

New post 28 Sep 2012, 05:56
Is this a 700 Category question ??
_________________
"When you want to succeed as bad as you want to breathe, then you’ll be successful.” - Eric Thomas
Intern
Intern
avatar
Joined: 01 Jun 2012
Posts: 18
Location: United States
Concentration: Nonprofit
GMAT 1: 720 Q48 V43
GPA: 3.83
Re: Sequence2  [#permalink]

Show Tags

New post 04 Nov 2012, 13:22
Bunuel wrote:
virtualanimosity wrote:
Q.If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find value of n

1.12
2.13
3.9
4.10


Nominator sum of first n even integers = \(n*(n+1)=50*51\)
Denominator sum of first n odd integers = \(n^2\)

\(\frac{50*51}{n^2}=\frac{51}{2}\)

\(n^2=100\)

\(n=10\)


Hi Bunuel,

How did you know that the sum of the terms in the denominator was \(n^2\)?
Current Student
User avatar
B
Joined: 03 Sep 2012
Posts: 372
Location: United States
Concentration: Healthcare, Strategy
GMAT 1: 730 Q48 V42
GPA: 3.88
WE: Medicine and Health (Health Care)
Re: If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find  [#permalink]

Show Tags

New post 04 Nov 2012, 22:17
2
Quote:
How did you know that the sum of the terms in the denominator was ?



Sum of n terms of an A.P. = n/2 { 2a+(n-1)d}

...

n/2 { 2x1 + (n-1)2}

: n/2 { 2 + 2n - 2}

: n/2 x 2n = n^2

Because the Sum of the first 50 even numbers can be calculated using the same formula to be 2550 , we get the equation:

2550/n^2 = 51/2

and solving for n we get n = 10.


You could also attack this question by plugging in the values in the answer choices :

Given one choice is 10 , we can easily write down the first 10 odd numbers to be : 1 3 5 7 9 11 13 15 17 19 .. So their sum = 10/5 x (A+L) = 10/5 x 20 = 40 ... Divide 2550 by 40 to get the desired ratio...


Hope this helps
_________________
"When you want to succeed as bad as you want to breathe, then you’ll be successful.” - Eric Thomas
Manager
Manager
avatar
Joined: 25 Jun 2012
Posts: 61
Location: India
WE: General Management (Energy and Utilities)
Re: If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find  [#permalink]

Show Tags

New post 05 Nov 2012, 02:54
1
Sn=n/2(2a+(n-1)d)...(1)

Here (2+4+...+50th Term)
n=50
a=2
d=2
Putting this in eqn (1) we get numerator = 25*102

Now for denominator,
n=n
a=1
d=2
putting this values in eqn(1) we get denominator = n*n

Now keeping in question stem,
25*102/n*n = 51/2

n = 10
Intern
Intern
avatar
Joined: 25 Jun 2012
Posts: 29
Re: If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find  [#permalink]

Show Tags

New post 02 Dec 2012, 08:56
bhavinshah5685 wrote:
Sn=n/2(2a+(n-1)d)...(1)

Here (2+4+...+50th Term)
n=50
a=2
d=2
Putting this in eqn (1) we get numerator = 25*102

Now for denominator,
n=n
a=1
d=2
putting this values in eqn(1) we get denominator = n*n

Now keeping in question stem,
25*102/n*n = 51/2

n = 10


I can't tell based on this equation what a is in the highlighted equation and what operation we are performing on it. Based on what seems to be happening, it is the first number of the sequence and that is it, the 2 didn't appear to do anything in this equation. help appreciated.
Manager
Manager
avatar
Joined: 22 Aug 2014
Posts: 136
Re: If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find  [#permalink]

Show Tags

New post 09 May 2015, 05:28
GMAT TIGER wrote:
virtualanimosity wrote:
Q.If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find value of n

1.12
2.13
3.9
4.10


Sum of 2+4+....+100 = 2(1+2+3+....+50) = 2(50x51/2) = 50x51

(50x51)/(1+3+5+....n terms) = 51/2
100 = 1+3+5+....n terms
100 = n (First term + last term)/2
100 = n (1 + 19)/2
n = 10



Hey ,
how did u get 19 as last term?
please explain!
:oops: :oops:
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 13262
Re: If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find  [#permalink]

Show Tags

New post 19 Oct 2018, 10:21
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 Club Bot
Re: If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find   [#permalink] 19 Oct 2018, 10:21
Display posts from previous: Sort by

If (2+4+6+....50 terms)/(1+3+5+....n terms)=51/2, then find

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





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