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

 It is currently 13 Dec 2019, 02:51 ### 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

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  # Two interconnected, circular gears travel at the same circumferential

Author Message
TAGS:

### Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 59722
Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

4
16 00:00

Difficulty:   65% (hard)

Question Stats: 52% (01:36) correct 48% (01:45) wrong based on 286 sessions

### HideShow timer Statistics

Two interconnected, circular gears travel at the same circumferential rate. If Gear A has a diameter of 30 centimeters and Gear B has a diameter of 50 centimeters, what is the ratio of the number of revolutions that Gear A makes per minute to the number of revolutions that Gear B makes per minute?

(A) 3:5

(B) 9:25

(C) 5:3

(D) 25:9

(E) Cannot be determined from the information provided

_________________
Intern  S
Joined: 30 May 2015
Posts: 37
WE: Analyst (Internet and New Media)
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

1
the bigger the diameter, the more distance wheel covers per revolutions OR lesser the revolutions wheel takes to cover the same distance. Going by this, rev. is inversely proportional to the diameter. Hence, $$\frac{(rev. of A)}{(rev. of B)}$$ =$$\frac{(diameter of B)}{(diameter of A)} =\frac{3}{5}$$
Director  D
Joined: 05 Mar 2015
Posts: 978
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

Bunuel wrote:
Two interconnected, circular gears travel at the same circumferential rate. If Gear A has a diameter of 30 centimeters and Gear B has a diameter of 50 centimeters, what is the ratio of the number of revolutions that Gear A makes per minute to the number of revolutions that Gear B makes per minute?

(A) 3:5

(B) 9:25

(C) 5:3

(D) 25:9

(E) Cannot be determined from the information provided

Distance covered by A=2*pi*r--------->30*pi
Distance covered by B=2*pi*r--------->50*pi
since their rates are equal
ratio=30*pi/50*pi==3/5
Ans A
VP  P
Joined: 07 Dec 2014
Posts: 1217
Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

A rpm*30⫪=B rpm*50⫪
A rpm/B rpm=50⫪/30⫪=5/3
Veritas Prep GMAT Instructor V
Joined: 16 Oct 2010
Posts: 9876
Location: Pune, India
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

Bunuel wrote:
Two interconnected, circular gears travel at the same circumferential rate. If Gear A has a diameter of 30 centimeters and Gear B has a diameter of 50 centimeters, what is the ratio of the number of revolutions that Gear A makes per minute to the number of revolutions that Gear B makes per minute?

(A) 3:5

(B) 9:25

(C) 5:3

(D) 25:9

(E) Cannot be determined from the information provided

Smaller the diameter, more the number of revolutions made since the circumferential rate of travel is the same for both gears (this just means that they cross the same distance in the given time). So smaller diameter means smaller circumference and hence more complete circles of travel.
Circumference of A/Circumference of B = Number of revolutions of B/Number of revolutions of A

Number of revolutions of B/Number of revolutions of A $$= 30\pi/50\pi$$

Number of revolutions of A/Number of revolutions of B = 5/3

_________________
Karishma
Veritas Prep GMAT Instructor

SVP  B
Joined: 06 Nov 2014
Posts: 1870
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

2
1
Bunuel wrote:
Two interconnected, circular gears travel at the same circumferential rate. If Gear A has a diameter of 30 centimeters and Gear B has a diameter of 50 centimeters, what is the ratio of the number of revolutions that Gear A makes per minute to the number of revolutions that Gear B makes per minute?

(A) 3:5

(B) 9:25

(C) 5:3

(D) 25:9

(E) Cannot be determined from the information provided

Same circumferential rate means that a point on both the gears would take same time to come back to the same position again.
Hence in other words, time taken by the point to cover the circumference of gear A = time take by point to cover the circumference of gear B

Time A = 2*pi*25/Speed A
Time B = 2*pi*15/Speed B

Since the times are same,

50pi/Speed A = 30pi/Speed B
SpeedA/Speed B = 50pi/30pi = 5/3

Correct Option: C
Intern  B
Joined: 08 Jan 2017
Posts: 1
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

it is given that rate is same i.e. the distance covered by A & B is same i.e.
Distance=circumference*revolution
so we can derive this relation

30*A=50*B (pie is canceled out)
A/B= 5/3
Target Test Prep Representative G
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2809
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

Bunuel wrote:
Two interconnected, circular gears travel at the same circumferential rate. If Gear A has a diameter of 30 centimeters and Gear B has a diameter of 50 centimeters, what is the ratio of the number of revolutions that Gear A makes per minute to the number of revolutions that Gear B makes per minute?

(A) 3:5

(B) 9:25

(C) 5:3

(D) 25:9

(E) Cannot be determined from the information provided

We see that Gear A has a circumference of 30π and Gear B has a circumference of 50π.

Since Gear A will make more revolutions than Gear B, the ratio is 50π/30π = 5/3.

_________________

# Jeffrey Miller

Jeff@TargetTestPrep.com

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Manager  G
Joined: 07 Jun 2017
Posts: 160
Location: India
Concentration: Technology, General Management
GMAT 1: 660 Q46 V38 GPA: 3.6
WE: Information Technology (Computer Software)
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

The circumference of circle = 2*Pi*r
here 2*pi constant
the number of revolution A should be more
hence it should be 5:3
Intern  B
Joined: 23 Sep 2017
Posts: 19
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

Both gears travel at the same rate x centimeter/min
Gear A travel x centimeters = x/30 revolution per minute
Grear B travel x centimeters = x/50 revolutions per minute
=> Ratio = (x/30)/(x/50) = 5:3
Hope it clears Non-Human User Joined: 09 Sep 2013
Posts: 13742
Re: Two interconnected, circular gears travel at the same circumferential  [#permalink]

### Show Tags

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: Two interconnected, circular gears travel at the same circumferential   [#permalink] 27 Nov 2019, 07:34
Display posts from previous: Sort by

# Two interconnected, circular gears travel at the same circumferential  