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

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

Square Root

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Junior | Next Rank: 30 Posts
Posts: 22
Joined: Thu Oct 04, 2012 2:06 am
Thanked: 1 times
by Benni » Mon Oct 22, 2012 7:50 am
Hi Guys,

regarding OG 13, 157, Data Suffiency.

If n is a positive integer and k=5.1x10^n, what is value of k?
(1) 6000<k<500 000
(2) k²=2.601x10^9

OA is D.


What I dont get is. k²=2.601x10^9. Therefore k=Plus or Minus Squareroot of 2.601x10^9. So in my view 2 is not sufficient. My question therefore is: When do I have to take account of the negative square root and when do I ignore it.

Thanks
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |

GMAT/MBA Expert

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

by Brent@GMATPrepNow » Mon Oct 22, 2012 7:54 am
Benni wrote:Hi Guys,

regarding OG 13, 157, Data Suffiency.

If n is a positive integer and k=5.1x10^n, what is value of k?
(1) 6000<k<500 000
(2) k²=2.601x10^9

OA is D.


What I dont get is. k²=2.601x10^9. Therefore k=Plus or Minus Squareroot of 2.601x10^9. So in my view 2 is not sufficient. My question therefore is: When do I have to take account of the negative square root and when do I ignore it.

Thanks
You're right to say that the equation k²=2.601x10^9 tells is that k = sqrt(2.601x10^9) or k = -sqrt(2.601x10^9).
However, the question also tells us that k=5.1x10^n. Since 5.1x10^n must always have a positive value, we know that k must be positive.
If k is positive, then k cannot equal -sqrt(2.601x10^9).
So, k must = sqrt(2.601x10^9)

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Junior | Next Rank: 30 Posts
Posts: 22
Joined: Thu Oct 04, 2012 2:06 am
Thanked: 1 times

by Benni » Mon Oct 22, 2012 10:51 am
Thank you for your very quick reply. I appreciate it. Your explaination is just fantastic.

But if you could please take a look at OG 13, 167, Datasufficiency:

If n and k are positive integers, is sqrt(n+k) > 2sqrt(n)?
1) k > 3n
2) n + k > 3n
OA is A.

They square the inequality to n+k>2n saying n and k are positive.
But what about following example: sqrt9>sqrt 4? --> solution one 3>2 and solution two -3>-2.
Now by squaring the solution b is lost. And this drives me crazy. :( :( Why are we allowed to square here.

Thank you very much.
Ben
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

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

by Brent@GMATPrepNow » Tue Oct 23, 2012 6:53 am
Benni wrote:Thank you for your very quick reply. I appreciate it. Your explaination is just fantastic.

But if you could please take a look at OG 13, 167, Datasufficiency:

If n and k are positive integers, is sqrt(n+k) > 2sqrt(n)?
1) k > 3n
2) n + k > 3n
OA is A.

They square the inequality to n+k>2n saying n and k are positive.
But what about following example: sqrt9>sqrt 4? --> solution one 3>2 and solution two -3>-2.
Now by squaring the solution b is lost. And this drives me crazy. :( :( Why are we allowed to square here.

Thank you very much.
Ben
The problem is indicated above in blue.

The square root notation essentially asks us for the positive square root.
That is, sqrt(9) = 3 (but not -3)

A lot of students make the mistake of assuming that the equation x^2 = 9 is virtually identical to the equation x = sqrt(9). These two equations are not identical.

The equation x^2 = 9 has two solutions: x=3 and x=-3
The equation x = sqrt(9) has only one solution: x=3

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Junior | Next Rank: 30 Posts
Posts: 22
Joined: Thu Oct 04, 2012 2:06 am
Thanked: 1 times

by Benni » Tue Oct 23, 2012 6:59 am
Many thanks for your lovely explanation!. :)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1