inequality

This topic has expert replies
Source: — Data Sufficiency |

Legendary Member
Posts: 2326
Joined: Mon Jul 28, 2008 3:54 am
Thanked: 173 times
Followed by:2 members
GMAT Score:710

by gmatmachoman » Sun Mar 28, 2010 4:13 am
neoreaves wrote:If x and y are positive, is x^3 > y?
(1) Sq rt x > y
(2) x > y
IMO E

(1) Sq rt x > y

Does not give a definite Yes or No when 0<X<1 & X>1.

2) x > y

Does not give a definite Yes or No when 0<X<1 & X>1.

Example :
X= 0.25
sqrt X= 0.5
Y=0.2

For St 1:

Sq rt x > y
but ,is x^3 > y----->NO

Now change values of X> 1

is x^3 > y-----> YES

So A& D Ruled out

ST 2: x > y

Use the values of X in 2 cases where X is less than 1 & X greater than 1. We would get a indefinite answer. So B ruled out.

IMO E

It's a good question. Peope tend to pick D at first go assuming X & Y are integers. But , put a break & see it just says X& Y are positives. It could be that X&Y are fractions or decimals.

User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Mon Mar 15, 2010 6:15 am
Thanked: 32 times
Followed by:1 members

by eaakbari » Mon Mar 29, 2010 7:09 am
Stem :
x^3>y?

Since its cube we dont have to worry about the sign. Only numbers between 0 and 1.

Statement 1
Plug numbers as x can be various values it turns out insuff.

Statement 2
If its a number between 0 and 1 we have a contradiction

Hence E