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wawatan: Master | Next Rank: 500 Posts; Posts: 171; Joined: Sat May 03, 2008 3:51 pm; Thanked: 8 times

by wawatan » Tue May 20, 2008 2:39 pm

OA A

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Source: Beat The GMAT — Problem Solving | Tue May 20, 2008 2:39 pm

sxjain3: Junior | Next Rank: 30 Posts; Posts: 12; Joined: Thu Mar 20, 2008 5:23 am; Location: USA; Thanked: 1 times

by sxjain3 » Tue May 20, 2008 4:13 pm

root (.0026) = root(26)/root(10000) = root(26)/100 = ~5/100 = ~.05

It cannot be .06 as that would required the value in question to be root(.0036) or something very close.

Hope this helps.

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VP_Jim: GMAT Instructor; Posts: 1223; Joined: Thu May 01, 2008 3:29 pmFollowed by: 15 members; Location: Los Angeles, CA; Thanked: 185 times

by VP_Jim » Tue May 20, 2008 5:28 pm

I think the best way to do this one is to estimate. You should know that the square root of 25 is 5. So, since this is very close to the square root of .0025, the answer must be .05. Also, as pointed out, it's useful to know that it can't be any of the answers ending in 6 because that puts it closer to 36 than to 25.

Another way to do it is to work backwards, by squaring the answer choices. If they yield .0025, that's the answer.

If we take .05*.05, we get .0025. Try squaring the other answer choices, and they are way off.

Hope this helps!

Jim S. | GMAT Instructor | Veritas Prep

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VP_RedSoxFan: GMAT Instructor; Posts: 85; Joined: Thu May 01, 2008 12:56 pm; Location: Salt Lake City, UT; Thanked: 24 times; GMAT Score:750+

by VP_RedSoxFan » Wed May 21, 2008 8:09 am

I like the answers given, but if you decide to "plug numbers", you should do it intelligently, after some consideration since squaring some answer choices (not necessarily these) could be a little hairy.

My point is to start with your best guess rather than just moving from A to E sequentially until you find what you're looking for.

Ryan S.
| GMAT Instructor |
Elite GMAT Preparation and Admissions Consulting
www.VeritasPrep.com

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