GMAT Prep1 DS Question

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pushkin1982: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Wed Jun 23, 2010 10:28 pm

by pushkin1982 » Sat Aug 21, 2010 10:17 am

4) Machines X & Y can produce components at their respective rates. How many more hours does Y take than X to produce a certain number of components?

A) X & Y working together take 2/3 of the time taken by X.
B) Y working alone takes Twice the time taken by X.

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Source: Beat The GMAT — Data Sufficiency | Sat Aug 21, 2010 10:17 am

4GMAT_Mumbai: Master | Next Rank: 500 Posts; Posts: 161; Joined: Mon Apr 05, 2010 9:06 am; Location: Mumbai; Thanked: 37 times

by 4GMAT_Mumbai » Sat Aug 21, 2010 10:24 am

Hi,

Statement 1:

Let X take 30 hours to complete the job.

1/30 + 1/Y = 1/20

1/Y = 1/20 - 1/30

1/Y = 1/60

In this case, Y takes 60 hours to complete the job.

Thus, if Y takes twice the times that X takes, then working together, they will complete the work in 2/3rd of the time taken by X alone.

How many more hours does Y take than X (in absolute terms) ? cannot tell - insufficient

Statement 2: Just a restatement of what has been implied by statement 1 - insufficient.

Combining 1 & 2: Does not take us much further.

Guess, it is E.

Hope this helps. Thanks.

Naveenan Ramachandran
4GMAT, Dadar(W) & Ghatkopar(W), Mumbai

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