Is x^3 > y?

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crackgmat007: Legendary Member; Posts: 882; Joined: Fri Feb 20, 2009 2:57 pmFollowed by: 1 member; Thanked: 15 times; GMAT Score:690

by crackgmat007 » Sun May 10, 2009 7:26 pm

If x and y are positive, is x^3 > y?
(1) sqare root of x > y
(2) x > y

Can someone help me solve this pls? Tx. answer seems to be E

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Source: Beat The GMAT — Data Sufficiency | Sun May 10, 2009 7:26 pm

Sunshine85: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Tue Mar 31, 2009 11:38 pm; Thanked: 2 times

by Sunshine85 » Sun May 10, 2009 9:32 pm

In my opinion , Answer is E.

Stmt 1: Sqrt(x) > y. Divide the positive numbers into [0,1] & [1,infinity]
x^3 > y for x>1 & x^3<y for x<1. Not sufficient.

Stmt 2: x>y, This statement yeilds same result as the one stated above. Not Sufficient.

Using numbers:

Stmt 1:

Take x= 0.01, [Sqrt ( 0.01 ) = 0.1], take y = 0.09.
x^3= 0.000001, y= .09 Therefore, x^3 < y for x belongs to (0,1)

Take x = 4 [ sqrt (4) = 2] ,y=1

x^3 = 64, y = 1. Therefore x^3 > y

Stmt 2:

Take x= 0.1 & y= .09. x^3 <y

Take x=2, y=1. x^3>y

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