It is currently 19 Nov 2017, 04:07

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Is it Ok to take the roots first?For example, in question 1

Author Message
Intern
Joined: 21 Aug 2010
Posts: 5

Kudos [?]: 15 [0], given: 0

Is it Ok to take the roots first?For example, in question 1 [#permalink]

### Show Tags

28 Aug 2010, 13:49
1
This post was
BOOKMARKED
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:14) wrong based on 3 sessions

### HideShow timer Statistics

Is it Ok to take the roots first?For example, in question 1 the roots for statement 1 are 0 and 5. For statement II, 0 and -5

Data sufficiency
1) Is X=5?

(I) $$x^2$$ – 5x = 0
(II)$$2x^2$$ + 10x= 0

2) Is x = y?

(I) |x-2|= 5
(II) $$y^2$$ – 4y – 21=0

Kudos [?]: 15 [0], given: 0

Math Expert
Joined: 02 Sep 2009
Posts: 42246

Kudos [?]: 132652 [1], given: 12331

### Show Tags

28 Aug 2010, 14:16
1
KUDOS
Expert's post
briandoldan wrote:
Is it Ok to take the roots first?For example, in question 1 the roots for statement 1 are 0 and 5. For statement II, 0 and -5

Data sufficiency
1) Is X=5?

(I) $$x^2$$ – 5x = 0
(II)$$2x^2$$ + 10x= 0

2) Is x = y?

(I) |x-2|= 5
(II) $$y^2$$ – 4y – 21=0

I'm not sure that I understand your question... But as for the problems:

Is x=5?

(1) $$x^2-5x=0$$ --> $$x=0$$ OR $$x=5$$. Not sufficient, to answer whether $$x=5$$.

(2) $$2x^2+10x=0$$ --> $$x=0$$ OR $$x=-5$$. Here we know that $$x\neq{5}$$, hence sufficient.

Is x = y?

(1) $$|x-2|= 5$$. Clearly insufficient as no info about $$y$$. But from this statement we know that either $$x=7$$ or $$x=-3$$.

(2) $$y^2-4y-21=0$$. Clearly insufficient as no info about $$x$$. But from this statement we know that either $$y=7$$ or $$y=-3$$.

(1)+(2) Now, it's possible that both $$x$$ and $$y$$ equal to -3 (or 7) and in this case answer would be YES: $$x=y$$ BUT it's also possible $$x$$ to be -3 and $$y$$ to be 7 (or vise-versa) and in this case answer would be NO: $$x\neq{y}$$. Two different answers to the question, hence not sufficient.

Hope it helps.
_________________

Kudos [?]: 132652 [1], given: 12331

Intern
Joined: 21 Aug 2010
Posts: 5

Kudos [?]: 15 [0], given: 0

### Show Tags

28 Aug 2010, 14:23
Bunuel wrote:
briandoldan wrote:
Is it Ok to take the roots first?For example, in question 1 the roots for statement 1 are 0 and 5. For statement II, 0 and -5

Data sufficiency
1) Is X=5?

(I) $$x^2$$ – 5x = 0
(II)$$2x^2$$ + 10x= 0

2) Is x = y?

(I) |x-2|= 5
(II) $$y^2$$ – 4y – 21=0

I'm not sure that I understand your question... But as for the problems:

Is x=5?

(1) $$x^2-5x=0$$ --> $$x=0$$ OR $$x=5$$. Not sufficient, to answer whether $$x=5$$.

(2) $$2x^2+10x=0$$ --> $$x=0$$ OR $$x=-5$$. Here we know that $$x\neq{5}$$, hence sufficient.

Is x = y?

(1) $$|x-2|= 5$$. Clearly insufficient as no info about $$y$$. But from this statement we know that either $$x=7$$ or $$x=-3$$.

(2) $$y^2-4y-21=0$$. Clearly insufficient as no info about $$x$$. But from this statement we know that either $$y=7$$ or $$y=-3$$.

(1)+(2) Now, it's possible that both $$x$$ and $$y$$ equal to -3 (or 7) and in this case answer would be YES: $$x=y$$ BUT it's also possible $$x$$ to be -3 and $$y$$ to be 7 (or vise-versa) and in this case answer would be NO: $$x\neq{y}$$. Two different answers to the question, hence not sufficient.

Hope it helps.

Thanks a lot Bunuel. It helped a lot. =)

Regards

Kudos [?]: 15 [0], given: 0

VP
Joined: 17 Feb 2010
Posts: 1471

Kudos [?]: 789 [0], given: 6

### Show Tags

29 Aug 2010, 20:56
Bunuel, For the 1st question, I did not understand the highlighted part. How do we know that x is not equal to -5?

(2)$$2x^2 + 10x = 0$$ --> $$x = 0 or x = -5.$$ [highlight]Here we know that x # 5[/highlight], hence sufficient

Kudos [?]: 789 [0], given: 6

CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2757

Kudos [?]: 1909 [0], given: 235

Location: Malaysia
Concentration: Technology, Entrepreneurship
Schools: ISB '15 (M)
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35

### Show Tags

29 Aug 2010, 21:02
seekmba wrote:
Bunuel, For the 1st question, I did not understand the highlighted part. How do we know that x is not equal to -5?

(2)$$2x^2 + 10x = 0$$ --> $$x = 0 or x = -5.$$ [highlight]Here we know that x # 5[/highlight], hence sufficient

the question is : Is x = 5

(2)$$2x^2 + 10x = 0$$ --> $$x = 0 or x = -5.$$

=> x is not equal to 5. Hence it is sufficient to answer the question.
_________________

Fight for your dreams :For all those who fear from Verbal- lets give it a fight

Money Saved is the Money Earned

Jo Bole So Nihaal , Sat Shri Akaal

GMAT Club Premium Membership - big benefits and savings

Gmat test review :
http://gmatclub.com/forum/670-to-710-a-long-journey-without-destination-still-happy-141642.html

Kudos [?]: 1909 [0], given: 235

VP
Joined: 17 Feb 2010
Posts: 1471

Kudos [?]: 789 [0], given: 6

### Show Tags

29 Aug 2010, 21:05
I got so lost in the options that completely forgot abt the original question. thats silly... thanks a bunch.

Kudos [?]: 789 [0], given: 6

Re: DS Inequalities I   [#permalink] 29 Aug 2010, 21:05
Display posts from previous: Sort by