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From GMAT Prep (Roots)

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From GMAT Prep (Roots)

by aninditasivaram2406 » Tue Nov 13, 2007 1:14 pm
How does one go about handling such problems?

If x and y are positive, which of the following must be greater than 1/(x+y)1/2?
I. (x+y) 1/2/2x
II. (x1/2+y1/2)/(x+y)
III. (x1/2-y1/2)/(x+y)

P.S all the 1/2's denote a square root. Sorry abt the format!

Answer is Option 2 only (highlight to see)
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by pahwa » Tue Nov 13, 2007 7:08 pm
To handle such questions, best way in GMAT is plug in values.
Given x and y are positive, try pluging in values of x and y > 0

Also, pls use positive decimals also, as we have no idea if x and y are just integers.
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by nkumar » Thu Nov 15, 2007 3:42 am
I think one way is to square the n and d immediately to get (x+y)^1/2/x+y.
Note that x^1/2 + y^1/2 is always greater than (x+y)^1/2 so answer should be only II.
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