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

 It is currently 14 Dec 2018, 18:25

### 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 December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### Typical Day of a UCLA MBA Student - Recording of Webinar with UCLA Adcom and Student

December 14, 2018

December 14, 2018

10:00 PM PST

11:00 PM PST

Carolyn and Brett - nicely explained what is the typical day of a UCLA student. I am posting below recording of the webinar for those who could't attend this session.
• ### Free GMAT Strategy Webinar

December 15, 2018

December 15, 2018

07:00 AM PST

09:00 AM PST

Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

# Circular Gears P and Q start rotating at the same time at

Author Message
Senior Manager
Affiliations: SPG
Joined: 15 Nov 2006
Posts: 301
Re: How many seconds after the gears start rotating?  [#permalink]

### Show Tags

02 Jan 2011, 03:33
2

Q does 30 more rev per min than P does ... so it does 1/2 rev more each sec
for 6 rev more ... Q will thus need 6/0.5 = 12secs

30 more .... 60 secs
1/2 more ... 1 sec
6 more ... 12 secs

you can do this in under 40secs
Intern
Joined: 24 Jun 2010
Posts: 15
Re: How many seconds after the gears start rotating?  [#permalink]

### Show Tags

05 Jan 2011, 01:40
Gear P

60sec--10rev
1sec=1/6 rev

Gear Q
60 sec--40 rev
1sec=2/3 rev

Gear q-Gear p=6
x(1/6)-x(2/3)=6----'x' is sec

X=12---Ans D
Intern
Joined: 11 Nov 2010
Posts: 5
Re: How many seconds after the gears start rotating?  [#permalink]

### Show Tags

05 Jan 2011, 03:09
Gear P .... in 60 seconds 10 rev.... 1 sec 1/6 rev
gear Q .... in 60 seconds 40 rev.... 1 sec 40/60 =2/3 rev

Difference of rev in one sec = 2/3 - 1/6 = 1/2 rev

1/2 revolution more for Gear Q than P in 1 sec
1 revolution more for Gear Q than P in 2 sec
6 revolutions more for Gear Q than P = 2 * 6 = 12 seconds.

Director
Joined: 01 Feb 2011
Posts: 659
Re: Gmat prep circular gears  [#permalink]

### Show Tags

05 Aug 2011, 11:23
p - 10 rev/min

q - 40 rev/min

in x min , p would make 10x revolutions

q would make 40x revolutions

given 40x = 10x+6

=> x = 1/5 mins
=12 seconds

Intern
Joined: 27 Feb 2011
Posts: 40
Re: Revolutions per minute problem  [#permalink]

### Show Tags

05 Aug 2011, 12:26
gear p makes 1/6 rev per sec
gear q makes 2/3 rev per sec

assume t is time elapsed in seconds..

6 = 2t/3 - t/6 => t = 12 sec..
Intern
Joined: 03 Aug 2011
Posts: 4
Re: Gmat prep circular gears  [#permalink]

### Show Tags

05 Aug 2011, 13:27
Equation can be set up as follows
(40/60-10/60)x=6.
(30/60)x=6
1/2 x=6
x=12
Intern
Joined: 09 Oct 2011
Posts: 1
GMAT Prep PS: Circular Gears P and Q revolutions  [#permalink]

### Show Tags

10 Oct 2011, 03:18
Circular Gears P and Q start rotating at the same time at constant speeds. Gear P makes 10 revolutions per minute, and gear Q makes 40 revolutions per minute. How many seconds after the gears start rotating will gear Q have made exactly 6 more revolutions than gear P?

(A) 9
(B) 10
(C) 12
(D) 14
(E) 15
Intern
Joined: 22 Jul 2011
Posts: 7
GMAT 1: 660 Q48 V34

### Show Tags

10 Oct 2011, 05:28
I'll take shot. Answer is C:

Here is why:

Gear P makes 1 revolution for every 6 secs
Gear q makes 1 revolutions for every 1.5 secs; that means for every 6 secs it makes it makes 4 revolution

so p make 1 revolution for 6 secs and q 4 revs. diffrence 3. But we are asked for difference of 6 revs.

so doubling the above equation:
12secs - 2 revs -- P
12 secs - 8 revs - Q difference is 6.

Ans c.

HTH
Current Student
Status: :)
Joined: 29 Jun 2010
Posts: 105
WE: Information Technology (Consulting)

### Show Tags

10 Oct 2011, 05:33
jiv wrote:
1) Circular Gears P and Q start rotating at the same time at constant speeds. Gear P makes 10 revolutions per minute, and gear Q makes 40 revolutions per minute. How many SECONDS after the gears start rotating will gear Q have made exactly 6 more revolutions?
a) 9
b) 10
c) 12
d) 14
e) 15

Can anyone help me get this resolved?

Thanks

In one minute - Q makes 30 more revolutions than P (40-10).

.i.e. so if Q needs to make 6 revolutions more than P - 60 sec/5 = 12 sec.

Let me know if you have any questions
_________________

Thanks,
GC24

Please click Kudos ,if my post helped you

Director
Status: No dream is too large, no dreamer is too small
Joined: 14 Jul 2010
Posts: 520
Re: Circular Gears P and Q start rotating at the same time at  [#permalink]

### Show Tags

21 Dec 2011, 09:17
30 revelation in 60 seconds
so, 6 revelation in =[60/30]*6 = 12
Ans. D
_________________

Collections:-
PSof OG solved by GC members: http://gmatclub.com/forum/collection-ps-with-solution-from-gmatclub-110005.html
DS of OG solved by GC members: http://gmatclub.com/forum/collection-ds-with-solution-from-gmatclub-110004.html
100 GMAT PREP Quantitative collection http://gmatclub.com/forum/gmat-prep-problem-collections-114358.html
Collections of work/rate problems with solutions http://gmatclub.com/forum/collections-of-work-rate-problem-with-solutions-118919.html
Mixture problems in a file with best solutions: http://gmatclub.com/forum/mixture-problems-with-best-and-easy-solutions-all-together-124644.html

Manager
Joined: 13 May 2011
Posts: 231
WE 1: IT 1 Yr
WE 2: Supply Chain 5 Yrs
Re: Circular Gears P and Q start rotating at the same time at  [#permalink]

### Show Tags

21 Dec 2011, 10:17
after 60 sec Q makes 30 rev. more than p.
i. e. for q to make 6 rev. more, it will take (60*6)/30=12 sec.
Non-Human User
Joined: 09 Sep 2013
Posts: 9162
Re: Circular Gears P and Q start rotating at the same time at  [#permalink]

### Show Tags

11 Aug 2018, 13:42
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.
_________________
Re: Circular Gears P and Q start rotating at the same time at &nbs [#permalink] 11 Aug 2018, 13:42

Go to page   Previous    1   2   [ 32 posts ]

Display posts from previous: Sort by