GMAT Changed on April 16th - Read about the latest changes here

It is currently 22 Apr 2018, 01:10

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If 50-√7<x<50+√7, then x=?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
Math Revolution GMAT Instructor
User avatar
D
Joined: 16 Aug 2015
Posts: 5255
GMAT 1: 800 Q59 V59
GPA: 3.82
If 50-√7<x<50+√7, then x=? [#permalink]

Show Tags

New post 30 Mar 2018, 02:06
Expert's post
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

69% (00:59) correct 31% (01:03) wrong based on 39 sessions

HideShow timer Statistics

[GMAT math practice question]

If \(50-√7<x<50+√7\), then \(x=?\)

1) \(x\) is an odd integer
2) \(√x\) is an integer.
[Reveal] Spoiler: OA

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $79 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

1 KUDOS received
Intern
Intern
avatar
B
Joined: 12 Mar 2018
Posts: 3
Re: If 50-√7<x<50+√7, then x=? [#permalink]

Show Tags

New post 30 Mar 2018, 02:10
1
This post received
KUDOS
1) is not sufficient because x can be either 49 or 51
2) is sufficient because the only integer between 50−√7 and 50+√7 that is a perfect square (right word? not a native speaker) is 49
Manager
Manager
avatar
S
Joined: 05 Feb 2016
Posts: 107
Location: India
Concentration: General Management, Marketing
WE: Information Technology (Computer Software)
GMAT ToolKit User
Re: If 50-√7<x<50+√7, then x=? [#permalink]

Show Tags

New post 30 Mar 2018, 02:14
MathRevolution wrote:
[GMAT math practice question]

If \(50-√7<x<50+√7\), then \(x=?\)

1) \(x\) is an odd integer
2) \(√x\) is an integer.



since as 2<√7<3
so this can be simplied as 47.yy<x<52.zz


From1-->49 and 51 is possible so not A
From2-->only 49 is possible so B
SVP
SVP
User avatar
P
Joined: 26 Mar 2013
Posts: 1612
Reviews Badge CAT Tests
If 50-√7<x<50+√7, then x=? [#permalink]

Show Tags

New post 30 Mar 2018, 06:05
MathRevolution wrote:
[GMAT math practice question]

If \(50-√7<x<50+√7\), then \(x=?\)

1) \(x\) is an odd integer
2) \(√x\) is an integer.



It is nice to now \(\sqrt{7}\), We can also deduce it quickly

\(\sqrt{4}\) < \(\sqrt{7}\) < \(\sqrt{9}\)

2 < \(\sqrt{7}\) < 3.......You can notice it is close to 3.........So we estimate it

\(x\approx{2.8}\)

Question could be written as follows:

If \(47.2<x<52.8\), What is X??

1) \(x\) is an odd integer

X could be 51 or 49

Insufficient

2) \(√x\) is an integer

Only one value fits which is 49..........7 = \(\sqrt{49}\)

Sufficent

Answer: B
Expert Post
Top Contributor
SVP
SVP
User avatar
P
Joined: 12 Sep 2015
Posts: 2292
Location: Canada
Re: If 50-√7<x<50+√7, then x=? [#permalink]

Show Tags

New post 30 Mar 2018, 07:58
Expert's post
Top Contributor
MathRevolution wrote:
[GMAT math practice question]

If \(50 - √7 < x < 50 + √7\), then \(x = ?\)

1) x is an odd integer
2) √x is an integer.


Target question: What is the value of x?

Given: 50 - √7 < x < 50 + √7
√4 = 2
√9 = 3
So, we can say that √7 = 2.something

This means: 50 - 2.something < x < 50 + 2.something
Simplify to get: 47.something < x < 52.something

Statement 1: x is an odd integer
There are two values of x that satisfy statement 1 (since we also know that 47.something < x < 52.something):
Case a: x = 49
Case b: x = 51
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: √x is an integer
If √x is an integer, then x is a "perfect square"
So, some POSSIBLE values of x are: 1, 4, 9, 16, 25, 36, 49, 64, 81, etc
When we consider the given info (47.something < x < 52.something), we can conclude that x MUST equal 49
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent
_________________

Brent Hanneson – Founder of gmatprepnow.com

Image

Expert Post
Math Revolution GMAT Instructor
User avatar
D
Joined: 16 Aug 2015
Posts: 5255
GMAT 1: 800 Q59 V59
GPA: 3.82
Re: If 50-√7<x<50+√7, then x=? [#permalink]

Show Tags

New post 01 Apr 2018, 18:44
=>

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question.

Since \(2< √7< 3\), we have \(47< x < 53\) from the original condition ‘\(50-√7<x<50+√7’.\)

Condition 1)
As x is an odd integer, it could be \(49\) or \(51\).
Since we don’t have a unique solution, condition 1) is not sufficient.

Condition 2)
If \(√x\) is an integer, then x is the square of an integer.
49 is the only perfect square of an integer between \(47\) and \(53\).
Thus, \(x=49\)and condition 2) is sufficient.

Therefore, B is the answer.

Answer: B
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $79 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Re: If 50-√7<x<50+√7, then x=?   [#permalink] 01 Apr 2018, 18:44
Display posts from previous: Sort by

If 50-√7<x<50+√7, then x=?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.