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

It is currently 01 Sep 2015, 15:40
GMAT Club Tests

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

musical sacle has 13 notes each hainvg a different

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Current Student
avatar
Joined: 28 Dec 2004
Posts: 3387
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 14

Kudos [?]: 199 [0], given: 2

musical sacle has 13 notes each hainvg a different [#permalink] New post 02 Jun 2008, 21:13
1
This post was
BOOKMARKED
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

musical sacle has 13 notes each hainvg a different frequency. In scale notes are ordered by increasing frequency and highest note is twice the lowest. For each 12 lower frequencies the ratio of freuency to next higher is fixed constant. If lower frequency = 440 then frequency of 7th note in scale is?

a) 440 Sqr(2)
b) 440 Sqr(2^7)
c) 440 Sqr(2^12)
d)440 Sqr(2^14)
e)440 Sqr(2^16)
Expert Post
CEO
CEO
User avatar
Joined: 17 Nov 2007
Posts: 3574
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 433

Kudos [?]: 2352 [0], given: 359

GMAT ToolKit User Premium Member
Re: frequencies [#permalink] New post 02 Jun 2008, 22:58
Expert's post
A

Fast solution: answer has to be between 440 and 440*2. Only A works.

Usual solution:

\(r=f_n/f_{n-1}\) - a ratio

\(f_n=r*f_{n-1}=r^2*f_{n-2}=....=r^{n-1}*f_1\)

we know that

\(f_{13}=2*f_{1}=r^{12}*f_1\) --> \(r=2^{\frac{1}{12}}\)

So, \(f_7=r^{6}*f_1=2^{\frac{6}{12}}*f_1=2^{\frac{1}{2}}*f_1=\sqrt{2}*f_1\)
_________________

HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame

Current Student
avatar
Joined: 28 Dec 2004
Posts: 3387
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 14

Kudos [?]: 199 [0], given: 2

Re: frequencies [#permalink] New post 03 Jun 2008, 06:06
yes..i too logically knew that the ans will be A..

here is how the working is..

suppose lowest frequency is F..then the next higher frequency is r*F...the one after that is r^2*F..and so on until r^12*F

we are F=440
we are also told r^12*F=440*2

therefore r^12=2..we are asked about r^6? notice how sqrt(r^12)=r^6=sqrt(2)..

therefore the ans has to be 440sqrt(2)
Re: frequencies   [#permalink] 03 Jun 2008, 06:06
Display posts from previous: Sort by

musical sacle has 13 notes each hainvg a different

  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®.