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 Starts Oct 17
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Chris Peckover, 100th-Percentile GMAT Scorer

Oct 17 · Chris Peckover
Sat · 11:00 AM to 2:00 PM ET
Oct 20 · Chris Peckover
Tue, Thu · 8:00 to 10:00 PM ET
Oct 25 · Josh Braslow
Sun · 1:00 to 4:00 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemand 5 seats left Start anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

165+ EA score guarantee
$05-day trial no automatic billing
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 Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget 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.

Is sqrt(7x) an integer?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 20
Joined: Wed Dec 14, 2011 9:17 pm
by ank_1 » Mon Feb 13, 2012 9:42 pm
If square root of 28x is an integer, is square root of 7x an integer?

My Reasoning: 1> i would write 28x as 2^2*7x. Therefore sqrt(28x) to be integer x has to be 7*n*n. When i substitute value of x in equation sqrt(7x), i will get an integer.

But the answer on one of the test says it cannot be determined by this statement.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Legendary Member
Posts: 1084
Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members
Thanked: 158 times

by pemdas » Mon Feb 13, 2012 9:58 pm
ank_1 wrote:If square root of 28x is an integer, is square root of 7x an integer?

My Reasoning: 1> i would write 28x as 2^2*7x. Therefore sqrt(28x) to be integer x has to be 7*n*n. When i substitute value of x in equation sqrt(7x), i will get an integer.

But the answer on one of the test says it cannot be determined by this statement.
Sqrt(28x)=integer. Is Sqrt(7x)=integer?
Sqrt(28x)=Sqrt(2*2*7*x)=2*Sqrt(7x)

Thus, Sqrt(28x) must be an integer, only if Sqrt(7x) is an integer. Answer is Yes.
Last edited by pemdas on Mon Feb 13, 2012 11:00 pm, edited 1 time in total.
Success doesn't come overnight!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members
Location: Milpitas, CA
Thanked: 1854 times
GMAT Score:770

by Anurag@Gurome » Mon Feb 13, 2012 10:01 pm
ank_1 wrote:If square root of 28x is an integer, is square root of 7x an integer?

My Reasoning: 1> i would write 28x as 2^2*7x. Therefore sqrt(28x) to be integer x has to be 7*n*n. When i substitute value of x in equation sqrt(7x), i will get an integer.

But the answer on one of the test says it cannot be determined by this statement.
If √(28x) = integer, then is √(7x) an integer?
√(28x) = 2√(7x)
So, for 2√(7x) to be an integer, √(7x) should also be an integer. So, this is sufficient and the answer to the question is "yes".
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 20
Joined: Wed Dec 14, 2011 9:17 pm

by ank_1 » Mon Feb 13, 2012 10:20 pm
@PEMDAS - sqrt(28x) cannot be 2sqrt(14x).

I agree with anurag.This question was on Kaplan test and it says the statement is insufficient.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 1084
Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members
Thanked: 158 times

by pemdas » Mon Feb 13, 2012 10:56 pm
omg, i didn't know which question you put in pm

again, that was a blunder, of course Sqrt(28x) doesn't fall into the written above. I will update it.thanks for correction.
ank_1 wrote:@PEMDAS - sqrt(28x) cannot be 2sqrt(14x).

I agree with anurag.This question was on Kaplan test and it says the statement is insufficient.
Success doesn't come overnight!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 979
Joined: Tue Apr 14, 2009 1:38 amFollowed by: 12 members
Location: Hyderabad, India
Thanked: 49 times
GMAT Score:700

by bubbliiiiiiii » Thu Feb 16, 2012 12:09 am
Anurag@Gurome wrote:
ank_1 wrote:If square root of 28x is an integer, is square root of 7x an integer?

My Reasoning: 1> i would write 28x as 2^2*7x. Therefore sqrt(28x) to be integer x has to be 7*n*n. When i substitute value of x in equation sqrt(7x), i will get an integer.

But the answer on one of the test says it cannot be determined by this statement.
If √(28x) = integer, then is √(7x) an integer?
√(28x) = 2√(7x)
So, for 2√(7x) to be an integer, √(7x) should also be an integer. So, this is sufficient and the answer to the question is "yes".
Hi Sir,

As per you post, I understand that since 2sqrt(7x) is an integer, sqrt(7x) has to be an integer.

How about sqrt(7x) having some non-integer value, for instance 3.5, then 2sqrt(7x) results to 7 which is an integer.

Please share your thoughts and help me understand what am I missing in evaluating the problem?
Regards,

Pranay
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1