• Free Practice Test & Review
How would you score if you took the GMAT

Available with Beat the GMAT members only code

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

• Award-winning private GMAT tutoring
Register now and save up to $200 Available with Beat the GMAT members only code • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code ## og math # 130 tagged by: Brent@GMATPrepNow This topic has 8 expert replies and 121 member replies Goto page chirpy Newbie | Next Rank: 10 Posts Joined 14 Jul 2013 Posted: 5 messages Fri Jul 26, 2013 12:15 am C is the correct answer. Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums! shubhamp Newbie | Next Rank: 10 Posts Joined 22 Apr 2014 Posted: 2 messages Top Reply Thu Apr 24, 2014 8:35 am 12/15*18/(15+18) = 12*33/15*18 =22/15 daboo343 Newbie | Next Rank: 10 Posts Joined 12 Dec 2013 Posted: 1 messages Top Reply Fri Feb 14, 2014 11:58 pm 22/15 (D) shubhamp Newbie | Next Rank: 10 Posts Joined 22 Apr 2014 Posted: 2 messages Thu Apr 24, 2014 8:35 am 12/15*18/(15+18) = 12*33/15*18 =22/15 daboo343 Newbie | Next Rank: 10 Posts Joined 12 Dec 2013 Posted: 1 messages Fri Feb 14, 2014 11:58 pm 22/15 (D) GMATinsight Legendary Member Joined 10 May 2014 Posted: 1003 messages Followed by: 21 members Upvotes: 205 Thu Jul 24, 2014 5:57 am Quote: resilient wrote: working alone, printers x,y, and z can do a certain printing job, consistning of a large number of pages, 12, 15, and 18 hours, respectively. What is the ratio of the time it takes printer x to do the job, working at its rate, to 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 Let's assume the Total work in terms of "Work units" by assuming it a number which is a Common multiple (not essentially the LCM) of 12, 15 and 18. This exercise is specially beneficial in order to avoid the calculation of fraction. A common multiple of 12, 15 and 18 = 180 (One can also assume this number as 360, 540 etc. however the least is the best] Since the 180 units is done by X in 12 Hours, Y in 15 hours and X in 18 hours therefore - One hour of Printer X : 180/12 = 15 Units. - One hour of Printer Y : 180/15 = 12 Units. - One hour of Printer Z : 180/18 = 10 Units. - One hour of Printer Y and Z together : 12+10 = 22 Units. Total time taken by Y and Z to finish the work together = 180/22 = 90/11 hours So the Required ratio is: 12/(90/11) = 22/15 Answer: Option D _________________ Bhoopendra Singh & Sushma Jha - Founder "GMATinsight" Testimonials e-mail: info@GMATinsight.com I Mobile: +91-9999687183 / +91-9891333772 To register for One-on-One FREE ONLINE DEMO Class Call/e-mail One-On-One Private tutoring fee - US$40 per hour & for FULL COURSE (38 LIVE Sessions)-US\$1000

dmv Newbie | Next Rank: 10 Posts
Joined
22 Jul 2014
Posted:
3 messages
Thu Jul 24, 2014 12:24 am
1/15 +1/18 = 11/90

Y and Z together = 90/11

therefore ratio = 12/1/90/11 = 22/15

visufun Newbie | Next Rank: 10 Posts
Joined
13 Jan 2014
Posted:
1 messages
Tue Jul 22, 2014 11:22 pm
Dont jump and solve this problem straight away.

You can straight away eliminate choices a, b and c as those choices dosen't make any sense. ( time for A to complete the job will always be greater than time for B & C working together)

Now we are left with D and E.

pick a comfortable number which divides 12, 15 and 18. I chose 180. time taken for printing 180 units will be,

A - 15
B - 12
C - 10

180/15 by 180/(12 +10) = 22/15

Joseph_Alexander Senior | Next Rank: 100 Posts
Joined
14 May 2014
Posted:
45 messages
1
Mon Jul 07, 2014 11:30 pm
resilient wrote:
hmm still not seeing the picture. What I am trying to grasp is why the flip of the combined rates. It doesnt make sense to me and goes against what is taught with mahattan gmat. confused

thank you
Hi resilent!

I got the same answer as yours. Noticed that 12, 15 and 18 is the time they take to complete a job and it is not their speed. So assuming that the work is 180, their speed would be 15, 12 and 10. Now if you use 15, 12 and 10, you won't have to flip!

kshitijhbti Newbie | Next Rank: 10 Posts
Joined
23 Jan 2014
Posted:
2 messages
Mon Feb 03, 2014 12:07 am

Time taken by x = 12

Time taken y and z to work together = (18*15)/(18+15) = 270/33 = 90/11

Ratio= x/(y+z)= 12/(90/11) = 12*11/ 90 = 22/15

sansulee Junior | Next Rank: 30 Posts
Joined
01 Nov 2013
Posted:
12 messages
Test Date:
December 4th, 2013
Target GMAT Score:
650
GMAT Score:
590
Sun Nov 03, 2013 8:38 am
GMATGuruNY wrote:
resilient wrote:
working alone, printers x,y, and z can do a certain printing job, consisitning of a large number of pages, 12, 15, and 18 hours, respectively. What is the ratio of the time it takes printer x to do the job, working at its rate, to 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

qa is d. I dont see why C is wrong. I dont see why the solution flips the combined rate of y and z working together. help stuart?
I think that the easiest approach is to plug in a value for the job in order to determine everyone's respective rates.

Plug in job = 180.
Rate for x = w/t = 180/12 = 15/hour.
Rate for y = w/t = 180/15 = 12/hour.
Rate for z = w/t = 180/18 = 10/hour.
Combined rate of y+z = 12+10 = 22/hour.
Time for y+z = w/r = 180/22 = 90/11.
Ratio of (time x):(time y+z) = 12/(90/11) = 22/15.

Could you explain why the answer is D?

Aren't we supposed to take the ratio of the "rates" of these individual entities? (considering x as one and the combo of y-z as another entity)?

In that case, shouldn't the calculation go as:

1/12 / 33/15*18 = 15*18 / 33*12 ; eventually yielding 15/22 ?

Please correct me if I am wrong, so that I do not repeat the mistake.

Thanks!

_________________
Success is the ability to go from failure to failure without losing your enthusiasm.

### GMAT/MBA Expert

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3650 messages
Followed by:
81 members
267
GMAT Score:
760
Thu Oct 24, 2013 5:07 am
This thread would prove out to be an EPIC on BTG.

http://www.beatthegmat.com/og-math-130-t9128-105.html#699281

_________________
The mind is everything. What you think you become. â€“Lord Buddha

Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
yogesh_yadav Newbie | Next Rank: 10 Posts
Joined
20 Oct 2013
Posted:
1 messages
Wed Oct 23, 2013 4:32 am
22/15

prats14 Newbie | Next Rank: 10 Posts
Joined
21 Sep 2013
Posted:
2 messages
1
Tue Sep 24, 2013 9:37 am
22/15

leekaru14 Newbie | Next Rank: 10 Posts
Joined
18 Sep 2013
Posted:
7 messages
Wed Sep 18, 2013 12:21 am
I divide the workload into 180 widgets.
In one hour:
- Printer x can finish: 180/12 = 15 widgets.
- Printer y can finish: 180/15 = 12 widgets.
- Printer z can finish: 180/18 = 10 widgets.
So in one hour y and z can finish: 22 widgets. Therefore it takes them 190/22 = 90/11 hours to finish the work.
So the ratio is: 12/(90/11) = 22/15

### Best Conversation Starters

1 lheiannie07 116 topics
2 LUANDATO 67 topics
3 swerve 66 topics
4 ardz24 61 topics
5 AAPL 59 topics
See More Top Beat The GMAT Members...

### Most Active Experts

1 Scott@TargetTestPrep

Target Test Prep

213 posts
2 Brent@GMATPrepNow

GMAT Prep Now Teacher

177 posts
3 Jeff@TargetTestPrep

Target Test Prep

168 posts
4 Rich.C@EMPOWERgma...

EMPOWERgmat

133 posts
5 GMATGuruNY

The Princeton Review Teacher

126 posts
See More Top Beat The GMAT Experts