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og math # 130

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by shingik » Tue Jul 12, 2011 3:02 pm
BTW --work problems are just one of those you should know the formula to solving for time (TIME A * TIME B divided by TIME A + TIME B) when given discrete simultaneous rates. Read up on this because it will save you a bunch of time from trying to figure out what the heck will be going on with which rate etc. It's kinda like triangle problems. You will eventually solve them but you really should not be inventing the wheel during the test. I think the GMAT just wants you to be able to recognize which type of problem you are working with and apply very simple mathematics.
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by raamjee » Tue Jul 12, 2011 9:52 pm
rate o x= 1/12
rate of y and z combined = 1/15+1/18 = 33/15.18

ratios is

22/15

option is D
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by astvansh » Thu Jul 21, 2011 12:53 am
c
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by abhisays » Tue Jul 26, 2011 12:36 am
The answer is D.
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by olegpoi » Thu Jul 28, 2011 11:45 am
D 22/15
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by ashhchdg » Tue Aug 16, 2011 3:32 pm
D 22/15

X does 1/12th of work in an hour.
Y+Z together do 1/18 and 1/15 of work together in an hour.
Simplifying they both together do 11/90 th of work.
Therefore they will complete the work in 90/11 if they work together

now the ratio asked is (12*11)/90---->22/15
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by JS_2 » Mon Aug 22, 2011 10:21 pm
22/15
Just reverse the time to rate for Y & Z. add the rates 1/y+1/z
Then reciprocal of 1/y and 1/x gives time taken by y and z together to complete the job..
Thats it..Ans = time taken by x/time taken by y and z together.
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by Deependra1 » Tue Aug 23, 2011 7:47 pm
ANSWER: D
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by navami » Thu Sep 08, 2011 12:29 pm
22/15
This time no looking back!!!
Navami
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by parul9 » Sun Sep 18, 2011 9:42 am
The answer is D.
However, I got it wrong. Thought it to be C.
Thought we had to find the ratio of rates and not the total time!

Key Takeaway: *Read* the question! X-(
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by way2ashish » Tue Sep 27, 2011 8:59 am
Correct answer is definitely D
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by ritzzzr » Tue Oct 11, 2011 10:23 pm
Work done by x in 1 hour = 1/12
Work done by y and z in 1 hour = 1/15+1/18=11/90

so total time taken by both to complete the job =90/11 hrs

time taken by x /time taken by a & b = 18/(90/11)=22/15


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?
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by olylo » Thu Oct 13, 2011 1:25 am
Answer is 22/15
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by dvinoth86 » Mon Oct 17, 2011 9:45 am
Best way to save time on such problems is to remove the fraction part by assuming the work as a LCM of the time taken to complete the work and then find individual work done/unit time. This has been explained earlier by Farooq.

Working with numbers definitely saves time when compared to working with fractions
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by rijul007 » Tue Oct 18, 2011 7:38 pm
Let us say the printer needs to print 180 pages.
Then,
the rate at which printer x works => 180/12 => 15 pages/hr
the rate at which printer y works => 180/15 => 12 pages/hr
the rate at which printer z works => 180/18 => 10 pages/hr
the rate at which printers y and z work => 10+12 => 22 pages/h

ratio of time taken by printer x to printer y and z together => (180/15)/(180/22) => 22/15
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