GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 22 Oct 2019, 17:27

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# If x is a nonzero number, which of the three numbers x, 1/x

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 21 Oct 2013
Posts: 411
If x is a nonzero number, which of the three numbers x, 1/x  [#permalink]

### Show Tags

Updated on: 29 Mar 2014, 09:47
1
2
00:00

Difficulty:

45% (medium)

Question Stats:

63% (01:24) correct 37% (01:27) wrong based on 184 sessions

### HideShow timer Statistics

If x is a nonzero number, which of the three numbers x, 1/x and x^2 is greatest?

(1) -1 < x < 1
(2) x is negative

Hi, can anyone explain St(2), please.

Originally posted by goodyear2013 on 29 Mar 2014, 06:05.
Last edited by Bunuel on 29 Mar 2014, 09:47, edited 1 time in total.
Edited the question.
Math Expert
Joined: 02 Sep 2009
Posts: 58427
Re: If x is a nonzero number, which of the three numbers x, 1/x  [#permalink]

### Show Tags

29 Mar 2014, 09:49
3
If x is a nonzero number, which of the three numbers x, 1/x and x^2 is greatest?

(1) -1 < x < 1. If x=1/2, then x=1/2, 1/x=2, and x^2=1/4, so 1/x has the greatest value but if x is negative, then both x and 1/x are negative and x^2=positive, so x^2 has the greatest value. Not sufficient.

(2) x is negative. For negative x both x and 1/x are negative and x^2=positive, so x^2 has the greatest value. Sufficient.

Hope it's clear.
_________________
e-GMAT Representative
Joined: 04 Jan 2015
Posts: 3078
Re: If x is a nonzero number, which of the three numbers x, 1/x  [#permalink]

### Show Tags

26 May 2015, 23:46
1
sidney123 wrote:
If x is a nonzero number, which of the three numbers x, 1/x, and x^2 is greatest?

1. -1<X<1

2. x is negative.

St. 1 x=-1/2 and x=1/2 yield different results. Not Sufficient

St.2 x=-2 and x=-1/2 yield different result. NS.

St.1 and St.2 -1<x<0, definite result x^2 > x > 1/x...Gmat prep Q. Says B..cannot get their explanation.

C..should be the answer for me

Hi sidney123,

1. Whenever you come across with such questions, look out for expressions which are independent of the sign of their base variables. In this question $$x^2$$ is independent of the sign of $$x$$. It will be always be non-negative irrespective of the sign of $$x$$. Any even power of a variable will be independent of the sign of the variable whereas any odd power of a variable will be dependent on the sign of the variable

2. Do keep in mind certain ranges where numbers behave differently.

a. For example in the range $$0 < x < 1$$, $$x^2 < x$$ and $$x < \frac{1}{x}$$.

b.Another such range is $$-1 < x < 0$$ where $$x^2 > x$$ but $$x^3 < x^2$$ and $$x > \frac{1}{x}$$

Hope this helps

Regards
Harsh
_________________
SVP
Joined: 06 Nov 2014
Posts: 1873
Re: If x is a nonzero number, which of the three numbers x, 1/x  [#permalink]

### Show Tags

27 May 2015, 11:11
1
If x is a nonzero number, which of the three numbers x, 1/x and x^2 is greatest?

(1) -1 < x < 1 We know that x is a fraction, but we don't know if it is negative or positive. If x is -1/2, then we have -1/2, -2, and 1/4 (x^2 is greatest). If x is 1/2 we have 1/2, 2, and 1/4, making (1/x greatest)
(2) x is negative We can answer this knowing the sign of x (again, take -1/2 as the example)
B
EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 15309
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: If x is a nonzero number, which of the three numbers x, 1/x  [#permalink]

### Show Tags

27 May 2015, 22:00
Hi sidney123,

Your approach to TEST VALUES is a good one, but you have to do the necessary work (on the pad, so you can "see" it) to make sure that you're selecting the correct answer.

Here, we're asked to consider X, 1/X and X^2.....We're asked which is GREATEST.

Fact 2 tells us that X is NEGATIVE....

Using your two examples, we'd end up with....

X = -2
1/X = -1/2
X^2 = (-2)^2 = 4
So X^2 is the greatest

X = -1/2
1/X = 1/(-1/2) = -2
X^2 = (-1/2)^2 = 1/4
So X^2 is the greatest

The two examples yield the SAME result. Based on what we're told in Fact 2, X will ALWAYS be NEGATIVE, 1/X will ALWAYS be NEGATIVE and X^2 will ALWAYS be POSITIVE, so the answer will ALWAYS be X^2. Thus, Fact 2 is SUFFICIENT.

As you continue to practice DS, whenever you think a Fact is insufficient, you should be able to quickly prove it. Doing that little bit of extra work can pick you up a LOT of points in the Quant section.

GMAT assassins aren't born, they're made,
Rich
_________________
Contact Rich at: Rich.C@empowergmat.com

The Course Used By GMAT Club Moderators To Earn 750+

souvik101990 Score: 760 Q50 V42 ★★★★★
ENGRTOMBA2018 Score: 750 Q49 V44 ★★★★★
Intern
Joined: 22 Jan 2014
Posts: 6
Re: If x is a nonzero number, which of the three numbers x, 1/x  [#permalink]

### Show Tags

27 May 2015, 22:53
Thankyou for all your input guys, really appreciate the time and effort taken to explain the simple problem. For some reason, I read the Q wrong(I don't know why?), I was looking at arranging x, 1/x and x^2 from smallest to greatest, in which case we need both statements. But the Q asks for which is greatest and stmt.2 is sufficient.
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 4018
Re: If x is a nonzero number, which of the three numbers x, 1/x  [#permalink]

### Show Tags

06 Feb 2019, 07:31
Top Contributor
goodyear2013 wrote:
If x is a nonzero number, which of the three numbers x, 1/x and x^2 is greatest?

(1) -1 < x < 1
(2) x is negative

Hi, can anyone explain St(2), please.

Given: x is a nonzero number

Target question: Which of the three numbers x, 1/x and x² is greatest?

Statement 1: -1 < x < 1
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several values of x that satisfy statement 1. Here are two:
Case a: x = 1/2. This means 1/x = 1/(1/2) = 2, and x² = (1/2)² = 1/4. In this case, the answer to the target question is 1/x is the greatest value
Case b: x = -1/2. This means 1/x = 1/(-1/2) = -2, and x² = (-1/2)² = 1/4. In this case, the answer to the target question is x² is the greatest value
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Aside: For more on this idea of testing values when a statement doesn't feel sufficient, read my article: http://www.gmatprepnow.com/articles/dat ... lug-values

Statement 2: x is negative
This means 1/x = 1/negative = negative, and x² = (negative,)² = positive.
Since x² is positive, and x and 1/x are negative, the answer to the target question is x² is definitely the greatest value
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Cheers,
Brent
_________________
Test confidently with gmatprepnow.com
Re: If x is a nonzero number, which of the three numbers x, 1/x   [#permalink] 06 Feb 2019, 07:31
Display posts from previous: Sort by