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

 It is currently 05 May 2015, 17:04

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A circular rim 28 inches in diameter rotates the same number

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Manager
Joined: 12 Mar 2003
Posts: 59
Followers: 1

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

A circular rim 28 inches in diameter rotates the same number [#permalink]  29 Jul 2003, 14:32
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
A circular rim 28 inches in diameter rotates the same number of inches per second as a circular rim 35 inches in diameter. If the smaller rim makes x revolutions per second, how many revolutions per minute does the larger rim make in terms of x?
SVP
Joined: 03 Feb 2003
Posts: 1608
Followers: 6

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

[#permalink]  29 Jul 2003, 20:26
Linear velocities of the points lying on both circles are the same.

X*14=Y35/2

Y=2*14*X/35 revolutions per second; it will rotate 60 times the number per minute

Y=2*14*60*X/35=48X
GMAT Instructor
Joined: 07 Jul 2003
Posts: 770
Location: New York NY 10024
Schools: Haas, MFE; Anderson, MBA; USC, MSEE
Followers: 13

Kudos [?]: 52 [0], given: 0

[#permalink]  29 Jul 2003, 22:54
stolyar wrote:
Linear velocities of the points lying on both circles are the same.

X*14=Y35/2

Y=2*14*X/35 revolutions per second; it will rotate 60 times the number per minute

Y=2*14*60*X/35=48X

Stolyar:

You are very analytical, but you need to do "sanity checks" on your answers. One circle is merely 20% larger than the other in scale. What makes you think that it is possible for one to rotate 48 times as fast as the other?

The answer that doesn't make any physical sense is usually wrong....
_________________

Best,

AkamaiBrah
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993

Manager
Joined: 24 Jun 2003
Posts: 146
Location: India
Followers: 1

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

[#permalink]  30 Jul 2003, 02:23
AkamaiBrah wrote:
stolyar wrote:
Linear velocities of the points lying on both circles are the same.

X*14=Y35/2

Y=2*14*X/35 revolutions per second; it will rotate 60 times the number per minute

Y=2*14*60*X/35=48X

Stolyar:

You are very analytical, but you need to do "sanity checks" on your answers. One circle is merely 20% larger than the other in scale. What makes you think that it is possible for one to rotate 48 times as fast as the other?

The answer that doesn't make any physical sense is usually wrong....

Akamai,

You forget that Y=48x is in revolutions per minute whereas x is in revolutions per second !!

If we use the same units, revolutions per second, then the larger circle's angular speed is (28/35)x=0.8x
Intern
Joined: 30 Jul 2003
Posts: 6
Followers: 0

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

[#permalink]  30 Jul 2003, 02:52
I think it should equal to X*28/35.

Regards,

Hopeful
Manager
Joined: 24 Jun 2003
Posts: 146
Location: India
Followers: 1

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

[#permalink]  30 Jul 2003, 03:05
hopeful wrote:
I think it should equal to X*28/35.

Regards,

Hopeful

Hopeful,

The questions clearly asks for the answer in revolutions per minute
Intern
Joined: 30 Jul 2003
Posts: 6
Followers: 0

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

[#permalink]  30 Jul 2003, 04:03
you are right! it shoud be X*60*28/35=48X

Thank you,

Hopeful
SVP
Joined: 03 Feb 2003
Posts: 1608
Followers: 6

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

[#permalink]  30 Jul 2003, 05:15
AkamaiBrah wrote:
stolyar wrote:
Linear velocities of the points lying on both circles are the same.

X*14=Y35/2

Y=2*14*X/35 revolutions per second; it will rotate 60 times the number per minute

Y=2*14*60*X/35=48X

Stolyar:

You are very analytical, but you need to do "sanity checks" on your answers. One circle is merely 20% larger than the other in scale. What makes you think that it is possible for one to rotate 48 times as fast as the other?

The answer that doesn't make any physical sense is usually wrong....

The question does not require to understand the physical sense directly. It uses different measures -- minutes and seconds. So, sanity cheking tells that the bigger circle rotates at X28/35 rps, a smaller rate that that of the first small circle (X rps). It is OK. But we have to translate the rate into rpm by multiplying it by 60.
GMAT Instructor
Joined: 07 Jul 2003
Posts: 770
Location: New York NY 10024
Schools: Haas, MFE; Anderson, MBA; USC, MSEE
Followers: 13

Kudos [?]: 52 [0], given: 0

[#permalink]  30 Jul 2003, 05:50
prashant wrote:
AkamaiBrah wrote:
stolyar wrote:
Linear velocities of the points lying on both circles are the same.

X*14=Y35/2

Y=2*14*X/35 revolutions per second; it will rotate 60 times the number per minute

Y=2*14*60*X/35=48X

Stolyar:

You are very analytical, but you need to do "sanity checks" on your answers. One circle is merely 20% larger than the other in scale. What makes you think that it is possible for one to rotate 48 times as fast as the other?

The answer that doesn't make any physical sense is usually wrong....

Akamai,

You forget that Y=48x is in revolutions per minute whereas x is in revolutions per second !!

If we use the same units, revolutions per second, then the larger circle's angular speed is (28/35)x=0.8x

Ahh. my bad. Apologies to Stolyar (although you still need to use sanity checks!).
_________________

Best,

AkamaiBrah
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993

[#permalink] 30 Jul 2003, 05:50
Similar topics Replies Last post
Similar
Topics:
A circular rim 28 inches in diameter rotates the same number of inches 1 12 Oct 2014, 21:31
2 A circular rim 28 inches in diameter rotates the same number of inches 4 30 Sep 2010, 19:38
29 A circular rim 28 inches in diameter rotates the same number 20 08 Jun 2008, 11:01
10 A circular rim 28 inches in diameter rotates the same number 6 08 Nov 2006, 15:15
A circular rim 28 inches in diameter rotates the same number 2 15 Apr 2006, 19:59
Display posts from previous: Sort by

# A circular rim 28 inches in diameter rotates the same number

 Question banks Downloads My Bookmarks Reviews Important topics

 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®.