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

 It is currently 03 Oct 2015, 21:13

### 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

# Working alone, printers X, Y, and Z can do a certain

Author Message
TAGS:
Senior Manager
Joined: 12 Mar 2006
Posts: 367
Schools: Kellogg School of Management
Followers: 2

Kudos [?]: 45 [3] , given: 3

Working alone, printers X, Y, and Z can do a certain [#permalink]  27 Jan 2007, 15:12
3
KUDOS
3
This post was
BOOKMARKED
00:00

Difficulty:

45% (medium)

Question Stats:

65% (02:32) correct 35% (01:28) wrong based on 247 sessions
Working alone, printers X, Y, and Z can do a certain printing job, consisting of a large number of pages, in 12, 15, and 18 hours, respectively. What is the ratio of the time it takes printer X to do the job, working alone at its rate, to the time it takes printers Y and Z to do the job, working together at their individual rates ?

(A) 4/11
(B) 1/2
(C) 15/22
(D) 22/15
(E) 11/4
[Reveal] Spoiler: OA
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 5952
Location: Pune, India
Followers: 1521

Kudos [?]: 8367 [3] , given: 192

Re: Working alone, printers X, Y, and Z can do a certain [#permalink]  23 Jan 2013, 19:02
3
KUDOS
Expert's post
leventg wrote:
Hi,

if somebody could help me what I am doing wrong here, it would be great:

1) I am calculating individual rates for all 3 printer and bring them onto the same denominator.
X = 1/12 = 30/360
Y = 1/15 = 24/360
Z = 1/18 = 20/360

2) Comparing the nominators of X with the sum of Y and Z, since they are now comparable.
30/(24+20) = 30/44 = 15/22

The ratio is X to (Y + Z) so it should be fine.
This would be answer (C) and not (D).
Why should I flip the nominator and denominator here?

RATES of X, Y and Z are 30/360, 24/360 and 20/360

Ratio of RATE of X:RATE of Y+Z = 30:44 = 15:22

The question asks for the ratio of TIME TAKEN = 1/15 : 1/22 = 22:15
(Time taken is the inverse of rate)
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Senior Manager Joined: 04 Jan 2006 Posts: 279 Followers: 1 Kudos [?]: 25 [1] , given: 0 [#permalink] 02 Feb 2007, 14:53 1 This post received KUDOS Rate(X) = 1/12 job/hour or 12 hour/job Rate(Y) = 1/15 job/hour Rate(Z) = 1/18 job/hour Rate(Y + Z) = 1/15 + 1/18 job/hour = (6 + 5)/90 = 11/90 job/hour This mean that Machine Y and Z can finish 11/90 job in one hour So how long will will take for Machine X to finish 11/90 job? Rate(X) = 12 hour/job Time(x) to do 11/90 job = 11/90 job x 12 hour/job = 11 x 12 /90 = 44/30 = 22/15 hours (D) is the answer. Intern Joined: 17 Dec 2012 Posts: 10 Followers: 0 Kudos [?]: 2 [1] , given: 0 Re: Working alone, printers X, Y, and Z can do a certain [#permalink] 23 Jan 2013, 12:12 1 This post received KUDOS Hi, if somebody could help me what I am doing wrong here, it would be great: 1) I am calculating individual rates for all 3 printer and bring them onto the same denominator. X = 1/12 = 30/360 Y = 1/15 = 24/360 Z = 1/18 = 20/360 2) Comparing the nominators of X with the sum of Y and Z, since they are now comparable. 30/(24+20) = 30/44 = 15/22 The ratio is X to (Y + Z) so it should be fine. This would be answer (C) and not (D). Why should I flip the nominator and denominator here? Thanks for your help in advance Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 5952 Location: Pune, India Followers: 1521 Kudos [?]: 8367 [1] , given: 192 Re: Working alone, printers X, Y, and Z can do a certain [#permalink] 24 Jan 2013, 03:40 1 This post received KUDOS Expert's post leventg wrote: Thanks for your fast reply Karishma, As this was still difficult for me to understand, I have created an easy example for better understanding. Let’s assume all printers take 12 hours. So printer Y and Z are doing the same job as printer X twice as fast. X = 1/12 (job/hours) Y = 1/12 (job/hours) Z = 1/12 (job/hours) Y+Z = 2/12 = 1/6 (job/hours) X : (Y+Z) = 1 : 2 => This ratio refers to the output. Regarding Time Taken, X makes in 12 hours 1 job and Y+Z are doing in 6 hours 1 job. So what you are saying is that we are comparing the hours and not the jobs right? And therefore the ratio of X : Y is 12 : 6, which is 2 : 1. Summarizing both steps: X : (Y+Z) = (1/12) : (2/12) = 1 : 2 => This ratio refers to the output. X : (Y+Z) = (1/12) : (1/6) = 2 : 1 => This ratio refers to the time. Referring to my example again: X = 12 hours Y+Z = 6 hours Ratio is not 12 : 6 or 2 : 1 because time taken is inverse to rate? Instead the Ratio is (1/12) : (1/6) = (6/12) = 1 : 2 Actually this TIME-IS-INVERSE-APPROACH is quite difficult to understand. I can apply it but still it is difficult to understand. May be it is just easier to divide 2 fractions. (Divide Y+Z by X). For an intuitive understanding of ratios approach, check out these posts: http://www.veritasprep.com/blog/2011/03 ... of-ratios/ http://www.veritasprep.com/blog/2011/03 ... os-in-tsd/ http://www.veritasprep.com/blog/2011/03 ... -problems/ _________________ Karishma Veritas Prep | GMAT Instructor My Blog Get started with Veritas Prep GMAT On Demand for$199

Veritas Prep Reviews

Senior Manager
Joined: 19 Jul 2006
Posts: 361
Followers: 1

Kudos [?]: 4 [0], given: 0

D

X takes 12 hrs

Y and Z together = (1/15) + (1/18) = 11/90 = 90/11 hrs

ratio = X /( YandZ) = 12 * (11/90) = 22/15
Manager
Joined: 10 Dec 2005
Posts: 112
Followers: 1

Kudos [?]: 3 [0], given: 0

Indeed D is the correct answer, got 22/15 by the exact same approach
_________________

"Live as if you were to die tomorrow. Learn as if you were to live forever." - Mahatma Gandhi

Intern
Joined: 17 Dec 2012
Posts: 10
Followers: 0

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

Re: Working alone, printers X, Y, and Z can do a certain [#permalink]  24 Jan 2013, 03:23

As this was still difficult for me to understand, I have created an easy example for better understanding.
Let’s assume all printers take 12 hours. So printer Y and Z are doing the same job as printer X twice as fast.

X = 1/12 (job/hours)
Y = 1/12 (job/hours)
Z = 1/12 (job/hours)
Y+Z = 2/12 = 1/6 (job/hours)

X : (Y+Z) = 1 : 2 => This ratio refers to the output.

Regarding Time Taken, X makes in 12 hours 1 job and Y+Z are doing in 6 hours 1 job.
So what you are saying is that we are comparing the hours and not the jobs right?
And therefore the ratio of X : Y is 12 : 6, which is 2 : 1.

Summarizing both steps:
X : (Y+Z) = (1/12) : (2/12) = 1 : 2 => This ratio refers to the output.
X : (Y+Z) = (1/12) : (1/6) = 12: 6 = 2 : 1 => This ratio refers to the time

Referring to my example again:
X = 12 hours
Y+Z = 6 hours
Ratio is not 12 : 6 or 2 : 1 because time taken is inverse to rate?
Instead the Ratio is (1/12) : (1/6) = (6/12) = 1 : 2

Actually this TIME-IS-INVERSE-APPROACH is quite difficult to understand. I can apply it but still it is difficult to understand. May be it is just easier to divide 2 fractions. (Divide Y+Z by X).

Last edited by leventg on 24 Jan 2013, 05:04, edited 1 time in total.
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 6696
Followers: 365

Kudos [?]: 82 [0], given: 0

Re: Working alone, printers X, Y, and Z can do a certain [#permalink]  19 Jan 2015, 12:29
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: Working alone, printers X, Y, and Z can do a certain   [#permalink] 19 Jan 2015, 12:29
Similar topics Replies Last post
Similar
Topics:
2 A person x working alone can complete a work in 10 days. A person Y .. 3 18 Jun 2015, 17:16
8 Working alone, pump A can empty a pool in 3 hours. Working alone, pump 10 23 Mar 2015, 05:34
16 Working alone, Printers X, Y, and Z can do a certain printin 10 05 Mar 2014, 01:16
6 While working alone at their constant rates computer X can process 240 11 29 Mar 2011, 03:36
2 Working alone, Printers X, Y, and Z can do a certain printin 3 25 Jun 2006, 14:10
Display posts from previous: Sort by