work problem

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nisha.menon294: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Sat Apr 10, 2010 8:33 am

work problem

by nisha.menon294 » Mon Apr 19, 2010 8:18 pm

Machines X and Y work together at their respective rates. How many more hours does it take Machine Y working alone to fill an order of a certain size than it takes machine X , working alone ?

1) Machines X and Y working together fill a production order of this size in two thirds of the time machine X, WORKING alone does
2)Machine Y working alone fills a production order of this size in twice the time that machine X ,working alone does .

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Source: Beat The GMAT — Data Sufficiency | Mon Apr 19, 2010 8:18 pm

liferocks: Legendary Member; Posts: 576; Joined: Sat Mar 13, 2010 8:31 pm; Thanked: 97 times; Followed by:1 members

by liferocks » Mon Apr 19, 2010 8:32 pm

IMO ans is E either of the statement will not provide the difference in hours
statement 1 we get when machine X completes 2/3 of the work machine Y completes 1/3 rd of the work
So machine Y takes twice the time that machine X ,working alone does.

statement 2 also provides the same relation as statement 1
both the statements provide the ratio of rate of work for machine X and Y but does not speak about the time takes in hours for either of them.

hence ans is E

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neoreaves: Master | Next Rank: 500 Posts; Posts: 208; Joined: Sun Sep 28, 2008 12:30 pm; Thanked: 22 times

by neoreaves » Tue Apr 20, 2010 8:25 am

IMO D

Lets say mahine x can finish an order in x hrs
machine y can finish an order in y hrs

what we need to know = x - y

1)
working together they will finish an order in xy/ (x+y) hrs

xy / (x+y) = 2x/3

solving this gave me
2x = y

thus x - y = x - 2x = -x

so sufficient

2) gives us 2x = y

thus sufficient

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harshavardhanc: Legendary Member; Posts: 526; Joined: Sat Feb 21, 2009 11:47 pm; Location: India; Thanked: 68 times; GMAT Score:680

by harshavardhanc » Tue Apr 20, 2010 11:38 am

neoreaves wrote:IMO D

Lets say mahine x can finish an order in x hrs
machine y can finish an order in y hrs

what we need to know = x - y

1)
working together they will finish an order in xy/ (x+y) hrs

xy / (x+y) = 2x/3

solving this gave me
2x = y

thus x - y = x - 2x = -x

so sufficient

2) gives us 2x = y

thus sufficient

X was a variable chosen for our convenience. They have not provided a value for it. Had we known what numbers X and Y stand for, we would have been able to say that D is the credited response.

Regards,
Harsha

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Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pm; Location: Toronto; Thanked: 1710 times; Followed by:614 members; GMAT Score:800

by Stuart@KaplanGMAT » Tue Apr 20, 2010 11:44 am

nisha.menon294 wrote:Machines X and Y work together at their respective rates. How many more hours does it take Machine Y working alone to fill an order of a certain size than it takes machine X , working alone ?

1) Machines X and Y working together fill a production order of this size in two thirds of the time machine X, WORKING alone does
2)Machine Y working alone fills a production order of this size in twice the time that machine X ,working alone does .

Here's an important rule for ds:

if a question asks for a specific value, you need at least 1 number somewhere in the information to solve.

Here, the question asks "how many more hours", i.e. we want an actual number, not just a ratio.

There are no actual numbers in the stem or either statement, therefore the answer must be (E).