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

Redeem

Value of n

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 298
Joined: Tue Feb 16, 2010 1:09 am
Thanked: 2 times
Followed by:1 members

Value of n

by Deepthi Subbu » Sun Sep 01, 2013 8:25 am
Is n > 6?

1. sqrt(n) > 2.5
2.n > sqrt(37)

[spoiler]I see A is sufficient. However, when it comes to st 2 , n > sqrt(37) translates to n^2 > 6 . So n is either greater than 6 or less than -6. So the answer must be A right?[/spoiler]
Top
Source: — Data Sufficiency |
User avatar
Legendary Member
Posts: 643
Joined: Wed Aug 14, 2013 4:27 am
Thanked: 48 times
Followed by:7 members

by vinay1983 » Sun Sep 01, 2013 8:49 am
Hmm, I feel it is as below:

Statement A

Sqrt(n) > 2.5

This can mean N can also be 6 or 7 or 8 Not sufficient


Statement B

N > sqrt (37)

Sqrt 37 yields little more than 6, hence N has to be more than 6 Sufficient
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!
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 Sep 01, 2013 9:56 am
Deepthi Subbu wrote:Is n > 6?

1) √n > 2.5
2) n > √37
Target question: Is 6 < n?

Statement 1: √n > 2.5
Since (2.5)² = 6.25, we know that √6.25 = 2.5
If √n is GREATER THAN 2.5, we know that n must be GREATER THAN 6.25
So, 6.25 < n
Since 6 < 6.25, we get 6 < 6.25 < n
So, it must be the case that Is 6 < n
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: n > √37
We know that √36 < √37
So, if √37 < n, we can write √36 < √37 < n
So, √36 < n
Since √36 = 6, we can be certain that 6 < n
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = D

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 234
Joined: Tue Jul 16, 2013 9:00 am
Location: West Virginia
Thanked: 9 times

by Java_85 » Sun Sep 01, 2013 11:50 am
Definitely D!
Top

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 Sep 01, 2013 1:10 pm
Hi Deepthi Subbu,

By definition, the square root of a number can only be POSITIVE.

So sqrt(37) must be positive and a little greater than 6.

By comparison, if you were told that N^2 > 6, then N COULD BE positive or negative.

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

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 Sep 01, 2013 1:13 pm
Hi vinay1983,

I hope you read through Bren't explanation, because you made a math mistake in your approach and it would have cost you this question.

Since (2.5)^2 = 6.25, Fact 1 proves that n > 6 and would be considered SUFFICIENT on its own!

You must be willing to do the necessary math (and do it correctly) if you want to hit 700+ on Test Day.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
User avatar
Legendary Member
Posts: 643
Joined: Wed Aug 14, 2013 4:27 am
Thanked: 48 times
Followed by:7 members

by vinay1983 » Sun Sep 01, 2013 8:42 pm
[email protected] wrote:Hi vinay1983,

I hope you read through Bren't explanation, because you made a math mistake in your approach and it would have cost you this question.

Since (2.5)^2 = 6.25, Fact 1 proves that n > 6 and would be considered SUFFICIENT on its own!

You must be willing to do the necessary math (and do it correctly) if you want to hit 700+ on Test Day.

GMAT assassins aren't born, they're made,
Rich
Yes you are right, this was a yes/no question.I mistook it for a value question!Point taken!
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 141
Joined: Fri Jun 24, 2011 4:35 am
Location: Edison
Thanked: 12 times
Followed by:1 members

by ani781 » Mon Sep 02, 2013 6:46 am
Hi ,
I am little confused with the statement D.
Why is it not that n > 36^1/2 => n > +6 / -6.

Is not sqrt of 36 = +/- 6 ?

Pls explain what am I missing here.
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 141
Joined: Fri Jun 24, 2011 4:35 am
Location: Edison
Thanked: 12 times
Followed by:1 members

by ani781 » Mon Sep 02, 2013 6:46 am
Hi ,
I am little confused with the statement D.
Why is it not that n > 36^1/2 => n > +6 / -6.

Is not sqrt of 36 = +/- 6 ?

Pls explain what am I missing here.
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 Sep 02, 2013 6:50 am
ani781 wrote:Hi ,
I am little confused with the statement D.
Why is it not that n > 36^1/2 => n > +6 / -6.

Is not sqrt of 36 = +/- 6 ?

Pls explain what am I missing here.
No, √36 does not equal 6 and -6
√n denotes the positive number whose square is n.
So, √36 = 6 (and only 6)

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 141
Joined: Fri Jun 24, 2011 4:35 am
Location: Edison
Thanked: 12 times
Followed by:1 members

by ani781 » Mon Sep 02, 2013 7:18 am
Thanks Brent, but please elaborate a little more... Is not -6 * -6 = 36 ?
Is it then |sqrt 36| which gives +6 / -6 ?
Where lies the difference between them ?
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 Sep 02, 2013 8:14 am
ani781 wrote:Thanks Brent, but please elaborate a little more... Is not -6 * -6 = 36 ?
Is it then |sqrt 36| which gives +6 / -6 ?
Where lies the difference between them ?
This all has to do with agreed-upon notation. From the Official Guide:

A square root of a number n is a number that, when squared, is equal to n. Every positive number n has two square roots, one positive and the other negative, but √n denotes the positive number whose square is n. For example, √9 denotes 3.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 141
Joined: Fri Jun 24, 2011 4:35 am
Location: Edison
Thanked: 12 times
Followed by:1 members

by ani781 » Mon Sep 02, 2013 9:24 am
Thanks a lot Brent.... This was a piece I had overlooked ... could you kindly guide me to any such more assumptions if any... I would be grateful...

Best Regards.
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 Sep 02, 2013 10:00 am
ani781 wrote:Thanks a lot Brent.... This was a piece I had overlooked ... could you kindly guide me to any such more assumptions if any... I would be grateful...

Best Regards.
I can't think of any other assumptions regarding square roots.
I guess there's this fact: the square root of a negative number is not a real number.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Post new topic Post Reply
• Page 1 of 1