Hi,
Let us look at statement 2:
If x >0 and we know that x^3 < x^2, then we can say that 0<x<1
To elaborate, the behavior of x^3 and x^2 across the different values of x are as follows:
==========
When x<0, x^3 < x^2
When x = 0, x^3 = x^2
When 0<x<1, x^3 < x^2
When x = 1, x^3 = x^2
When x > 1, x^3 > x^2
==========
Hence, the answer is D indeed ... Hope this helps.
Thanks.
One more OA wrong?
This topic has expert replies
Source: Beat The GMAT — Data Sufficiency |
-
4GMAT_Mumbai
- Master | Next Rank: 500 Posts
- Posts: 161
- Joined: Mon Apr 05, 2010 9:06 am
- Location: Mumbai
- Thanked: 37 times
-
kvcpk
- Legendary Member
- Posts: 1893
- Joined: Sun May 30, 2010 11:48 pm
- Thanked: 215 times
- Followed by:7 members
is x^2 < x ?adi_800 wrote:If x > 0, is x^2 < x ?
(1) 0.1 < x < 0.4
(2) x^3 < x^2
[spoiler]OA is D..
I got A[/spoiler]
is x^2-x<0
is x(x-1)<0?
Which means the question is asking is x<0 or x<1
Now,
(1) 0.1 < x < 0.4
clearly x<1. Hence SUFF
(2) x^3 < x^2
x^3-x^2<0
x^2(x-1)<0
x^2 canot be less than 0.
hence x-1<0
x<1
hence SUFF
pick D.
Hope this helps!!
"Once you start working on something,
don't be afraid of failure and don't abandon it.
People who work sincerely are the happiest."
Chanakya quotes (Indian politician, strategist and writer, 350 BC-275BC)
don't be afraid of failure and don't abandon it.
People who work sincerely are the happiest."
Chanakya quotes (Indian politician, strategist and writer, 350 BC-275BC)
GMAT/MBA Expert
-
Ian Stewart
- GMAT Instructor
- Posts: 2623
- Joined: Mon Jun 02, 2008 3:17 am
- Location: Montreal
- Thanked: 1090 times
- Followed by:355 members
- GMAT Score:780
Or yet another way to see that Statement 2 is sufficient: if x is positive, we can divide on both sides of the inequality by x without needing to worry about reversing the inequality. Doing that, you get x^2 < x, which is what we want to know.adi_800 wrote:If x > 0, is x^2 < x ?
(1) 0.1 < x < 0.4
(2) x^3 < x^2
[spoiler]OA is D..
I got A[/spoiler]
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com
ianstewartgmat.com
ianstewartgmat.com
-
Gurpinder
- Legendary Member
- Posts: 659
- Joined: Mon Dec 14, 2009 8:12 am
- Thanked: 32 times
- Followed by:3 members
Don't know what you did adi, but I get (D).adi_800 wrote:If x > 0, is x^2 < x ?
(1) 0.1 < x < 0.4
(2) x^3 < x^2
[spoiler]OA is D..
I got A[/spoiler]
We are simply checking whether X is a fraction or not by checking this --> x^2 < x
(1) 0.1 < x < 0.4
X is clearly a fraction because its between 0 and 1.
(2) x^3 < x^2
Since 3 x's are smaller than 2 x's, it HAS to be a fraction. Remember fraction squared is smaller than the original fraction. So here fraction cubed is smaller than fraction squared.
So the answer is (D).
"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.
- Alfred A. Montapert, Philosopher.
-
missrochelle
- Master | Next Rank: 500 Posts
- Posts: 117
- Joined: Wed Jun 09, 2010 7:02 am
Maybe she did what I did -- forgot that X had to be positive! In which case, X could be negative 1 and the answer would be A! Gotta read the statement carefully. I often screw up on that....
