BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Target Question & DS question

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Wed Dec 30, 2015 5:54 am

Target Question & DS question

by ashyacid » Sat Jan 02, 2016 11:46 pm
I was going through the DS videos on gmatprepnow, and in this video https://www.gmatprepnow.com/module/gmat- ... video/1100
he said that
Q: Is 4x < 3x
1. 3x + 4 < 3
2. 2x - 3 < 2

And he gave the answer that just 1 is sufficient. But in the previous videos it was told that we need to check the sufficiency, isn't the 2nd statement also sufficient enough to guess if x is negative or not?
What is actually the answer to this question?
Top
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pm
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:511 members
GMAT Score:800

by [email protected] » Sun Jan 03, 2016 9:53 am
Hi ashyacid,

This DS question is based on certain Number Property rules. You might find it easier to deal with if you 'rewrite' the question though...

We're asked if 4X < 3X....

Subtracting 3X from both sides 'rewrites' the question into...

Is X < 0? This is a YES/NO question.

1) 3X+4 < 3

3X < -1
X < -1/3

This Fact proves that X is ALWAYS NEGATIVE, so the answer to the question is ALWAYS YES.
Fact 1 is SUFFICIENT

2) 2X-3 < 2

2X < 5
X < 5/2

This Fact shows that X could be positive OR 0 OR negative. If X is positive or 0, then the answer to the question is NO. If X is negative, then the answer to the question is YES.
Fact 2 is INSUFFICIENT.

Rewriting the question isn't a necessary step to solving this question (the above explanations still apply if you leave the question unchanged), but you should look for opportunities to do so in the future.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Sun Jan 03, 2016 3:12 pm
ashyacid wrote:I was going through the DS videos on gmatprepnow, and in this video https://www.gmatprepnow.com/module/gmat- ... video/1100
he said that
Q: Is 4x < 3x
1. 3x + 4 < 3
2. 2x - 3 < 2

And he gave the answer that just 1 is sufficient. But in the previous videos it was told that we need to check the sufficiency, isn't the 2nd statement also sufficient enough to guess if x is negative or not?
What is actually the answer to this question?
Hi ashyacid,

What do you mean by "...in the previous videos it was told that we need to check the sufficiency?"

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Wed Dec 30, 2015 5:54 am

by ashyacid » Mon Jan 04, 2016 12:08 am
Brent@GMATPrepNow wrote:
ashyacid wrote:I was going through the DS videos on gmatprepnow, and in this video https://www.gmatprepnow.com/module/gmat- ... video/1100
he said that
Q: Is 4x < 3x
1. 3x + 4 < 3
2. 2x - 3 < 2

And he gave the answer that just 1 is sufficient. But in the previous videos it was told that we need to check the sufficiency, isn't the 2nd statement also sufficient enough to guess if x is negative or not?
What is actually the answer to this question?
Hi ashyacid,

What do you mean by "...in the previous videos it was told that we need to check the sufficiency?"

Cheers,
Brent
I was referring to this question. Because, we aren;t really getting an answer here either, but still the first statement is sufficient.
Attachments
Screen Shot 2016-01-04 at 1.34.30 PM.png
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Mon Jan 04, 2016 10:27 am
Sorry, I'm not sure what you're asking.
For your original question, the video explains that the answer is A.
Here's the screenshot:
Image

Statement 2 tells us that x < 2.5
So, x could equal 1, in which case x is NOT negative
OR x could equal -1, in which case x IS negative
Since we cannot answer the rephrased target question with certainty, statement 2 is NOT sufficient.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Master | Next Rank: 500 Posts
Posts: 137
Joined: Fri Nov 13, 2015 11:01 am
Thanked: 1 times
Followed by:2 members

by Amrabdelnaby » Thu Jan 07, 2016 1:11 pm
The only possible way for 4x to be less than 3x is when x is -ve.

so lets look at statement 2 2x - 3 < 2

after adding three to both sides u get 2x less than 5 which means that x is less than 2.5

x here can be any number less than 2.5, positive such as 1 or 2 or even a fraction or negative.

if x is positive then the answer to the question is no, and if x is -ve then the answer is yes. hence insufficient


ashyacid wrote:I was going through the DS videos on gmatprepnow, and in this video https://www.gmatprepnow.com/module/gmat- ... video/1100
he said that
Q: Is 4x < 3x
1. 3x + 4 < 3
2. 2x - 3 < 2

And he gave the answer that just 1 is sufficient. But in the previous videos it was told that we need to check the sufficiency, isn't the 2nd statement also sufficient enough to guess if x is negative or not?
What is actually the answer to this question?
Top
GMAT Instructor
Posts: 2630
Joined: Wed Sep 12, 2012 3:32 pm
Location: East Bay all the way
Thanked: 625 times
Followed by:119 members
GMAT Score:780

by Matt@VeritasPrep » Fri Jan 08, 2016 1:41 pm
Brent@GMATPrepNow wrote:Sorry, I'm not sure what you're asking.
I *think* he means that even if S1 is sufficient alone, you still need to check whether S2 is sufficient alone, but I'm not certain.
Top
Post new topic Post Reply
• Page 1 of 1