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Register now and save up to $200 Available with Beat the GMAT members only code • Free Trial & Practice Exam 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 ## og math # 130 tagged by: Brent@GMATPrepNow This topic has 8 expert replies and 121 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!!! Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums! bharat.bondalapati Junior | Next Rank: 30 Posts Joined 05 Apr 2013 Posted: 14 messages Upvotes: 3 Top Reply 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 _________________ Best, Bharat If you find my post helpful, please click on the 'Thank' icon. smvjkumar Junior | Next Rank: 30 Posts Joined 03 Jun 2012 Posted: 10 messages Test Date: Nov 10 Target GMAT Score: 750 GMAT Score: 590 Top Reply 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 _________________ The Biggest hurdle in the Path of success is the fear of failure bharat.bondalapati Junior | Next Rank: 30 Posts Joined 05 Apr 2013 Posted: 14 messages Upvotes: 3 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 _________________ Best, Bharat If you find my post helpful, please click on the 'Thank' icon. smvjkumar Junior | Next Rank: 30 Posts Joined 03 Jun 2012 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 _________________ The Biggest hurdle in the Path of success is the fear of failure jitsy Senior | Next Rank: 100 Posts Joined 19 Dec 2010 Posted: 51 messages Followed by: 2 members Upvotes: 11 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. _________________ If you appreciated my post or even just my time trying to help, please don't forget to click on 'Thanks' and say "Piece o' Cake mate" at the same time. 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? deepsea13 Junior | Next Rank: 30 Posts Joined 12 Jun 2011 Posted: 13 messages Followed by: 1 members Mon May 27, 2013 10:00 pm Answer D) 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 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 ### 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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rajeshsinghgmat Master | Next Rank: 500 Posts
Joined
08 Jan 2013
Posted:
171 messages
1
Thu Jan 10, 2013 5:52 am
22/15

ritzzzr Senior | Next Rank: 100 Posts
Joined
10 Oct 2011
Posted:
37 messages
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

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

mekoner Newbie | Next Rank: 10 Posts
Joined
15 Jul 2012
Posted:
2 messages
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?

robvspencer Newbie | Next Rank: 10 Posts
Joined
17 Dec 2012
Posted:
4 messages
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.

Thanked by: bnpetteway

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