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Register now and save up to $200 Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT 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 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Reach higher with Artificial Intelligence. Guaranteed Now free for 30 days Available with Beat the GMAT members only code ## og math # 130 tagged by: Brent@GMATPrepNow This topic has 8 expert replies and 124 member replies Goto page Kanav Puri Newbie | Next Rank: 10 Posts Joined 03 Oct 2012 Posted: 2 messages Tue Oct 09, 2012 11:09 pm 22/15.. pretty easy!!! siddhantlife Junior | Next Rank: 30 Posts Joined 14 Oct 2012 Posted: 10 messages Tue Oct 16, 2012 8:23 am my take: d ..easy one ritind Senior | Next Rank: 100 Posts Joined 21 Nov 2012 Posted: 47 messages Upvotes: 4 Test Date: 07/02/2013 Target GMAT Score: 750 Wed Nov 28, 2012 1:09 am x needs 12 hrs to do the job y and z needs = 1/(1/15 + 1/18) = 90/11 x : y+z = 12/(90/11) = 12*11/90 = 22/15 robvspencer Newbie | Next Rank: 10 Posts Joined 17 Dec 2012 Posted: 4 messages Upvotes: 1 Sat Dec 22, 2012 10:06 am Use work formula and this problem takes > minute. x = 12 y = 15 z = 18 need ratio of x to y + z formula for work = 1 / individual hours y + 1 / individual hours z = 1 / combined hours to complete or reciprocal of your answer = 1/15 + 1/18. Use bowtie method to add fractions = 33/270 or 270/33 since you then need to take reciprocal. Need x over this so 12 over 270/33 = 12 x 33/270 = 396 / 270. Dont need to reduce only plausible answer is 22/15. mekoner Newbie | Next Rank: 10 Posts Joined 15 Jul 2012 Posted: 2 messages Upvotes: 1 Sun Dec 23, 2012 8:30 am robvspencer wrote: Use work formula and this problem takes > minute. x = 12 y = 15 z = 18 need ratio of x to y + z formula for work = 1 / individual hours y + 1 / individual hours z = 1 / combined hours to complete or reciprocal of your answer = 1/15 + 1/18. Use bowtie method to add fractions = 33/270 or 270/33 since you then need to take reciprocal. Need x over this so 12 over 270/33 = 12 x 33/270 = 396 / 270. Dont need to reduce only plausible answer is 22/15. I don't understand the part where you flipped the 270/33. Why do you need o take the reciprocal? rajput.sushant Newbie | Next Rank: 10 Posts Joined 03 Jun 2012 Posted: 2 messages Target GMAT Score: 720 Mon Jan 07, 2013 8:01 am Since we know Work = Rate X Time work done is same by x,y,z i.e. lets say work done is 1 Rate at which x works Rx-----1/12 similarly Ry-----1/15 Rz-----1/18 When y and z work together their rate of doing a job...Ry+Rz-----1/15+1/18=11/90 Now Tx/Ty+z=Ry+z/Rx since work done is same, time is inversely proportional to rate. Tx/Ty+z=(11/90)/(1/12)=11*12/90=22/15 Thanks ritzzzr Senior | Next Rank: 100 Posts Joined 10 Oct 2011 Posted: 37 messages Upvotes: 2 Wed Jan 09, 2013 2:46 am Rate of work for x is 1/12 i.e. it will complete 1/12th of work in one hour Rate of work for y is 1/15 i.e. it will complete 1/15th of work in one hour Rate of work for z is 1/18 i.e. it will complete 1/18th of work in one hour Combined rate of work for y & z is 1/15 + 1/18 =(18 + 15 )/270 = 11/90 i.e. both complete 11/90th of work in one hour So total time taken by both of them to complete the work is 90/11 SO ratio of time taken by X & by y & Z together =12/(90/11) =22/15 rajeshsinghgmat Master | Next Rank: 500 Posts Joined 08 Jan 2013 Posted: 171 messages Upvotes: 1 Thu Jan 10, 2013 5:52 am 22/15 ### GMAT/MBA Expert Jim@StratusPrep MBA Admissions Consultant Joined 11 Nov 2011 Posted: 2278 messages Followed by: 265 members Upvotes: 660 GMAT Score: 770 Thu Jan 10, 2013 5:58 am Crazy that this post is still getting responses after 5 years! _________________ GMAT Answers provides a world class adaptive learning platform. -- Push button course navigation to simplify planning -- Daily assignments to fit your exam timeline -- Organized review that is tailored based on your abiility -- 1,000s of unique GMAT questions -- 100s of handwritten 'digital flip books' for OG questions -- 100% Free Trial and less than$20 per month after.
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smvjkumar Junior | Next Rank: 30 Posts
Joined
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Posted:
10 messages
Test Date:
Nov 10
Target GMAT Score:
750
GMAT Score:
590
Sat Apr 06, 2013 10:56 am
Amount of work done by printer X in 1 hour = 1/12
Amount of work done by printer Y in 1 hour = 1/15
Amount of work done by printer Z in 1 hour = 1/18

Work done by Y & Z in 1 hour = ((1/15)+(1/18))
= (11/90)
SO actual time taken by Y & Z together = 90/11

ratio of X/ (Y + Z) = 12 / (90/11)
= 2/(15/11)
= 22/15

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bharat.bondalapati Junior | Next Rank: 30 Posts
Joined
05 Apr 2013
Posted:
14 messages
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Sun Apr 07, 2013 9:09 am
Y and Z together do the job in

1/15 + 1/18 = 11/90

Therefore, Y and Z together do the job in 90/11 hours

12 : 90/11
which is 22:15

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sayanpaul Junior | Next Rank: 30 Posts
Joined
18 Dec 2012
Posted:
20 messages
Tue Apr 09, 2013 6:40 am
Time taken for x = 12 hrs
Time taken for y = 15 hrs
Time taken for z = 18 hrs

Let the time taken for both y and z to complete the task = t
therefore, 1/t = 1/15 + 1/18 = 11/90
hence, t = 90/11

therefore, x:t = 12/90/11 = (12*11)/90 = 22/15

deepsea13 Junior | Next Rank: 30 Posts
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Mon May 27, 2013 10:00 pm

Explanation:

For x: 1/12

For y and z combined: 1/15 + 1/18

Ratio x/(y+z) = (1/12)/(1/15 + 1/18)

After you do the math it comes to 15/22.

Flip this and you'll get the time taken to do the whole job which comes to 22/15

kingkavalli Newbie | Next Rank: 10 Posts
Joined
01 Mar 2013
Posted:
1 messages
Thu Jul 18, 2013 7:24 am
Doesn't this solution imply that x is faster than y and z combined? This seems counter intuitive. x:y&z
22:15?

jitsy Senior | Next Rank: 100 Posts
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Posted:
51 messages
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Thu Jul 18, 2013 8:29 am
kingkavalli wrote:
Doesn't this solution imply that x is faster than y and z combined? This seems counter intuitive. x:y&z
22:15?
I'll explain. No, x is taking 22 hrs as per the solution vs 15 for y and z. X is slower than y and z combined.

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