GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 16 Nov 2018, 08:27

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 in November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • Free GMAT Strategy Webinar

     November 17, 2018

     November 17, 2018

     07:00 AM PST

     09:00 AM PST

    Nov. 17, 7 AM PST. Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.
  • GMATbuster's Weekly GMAT Quant Quiz # 9

     November 17, 2018

     November 17, 2018

     09:00 AM PST

     11:00 AM PST

    Join the Quiz Saturday November 17th, 9 AM PST. The Quiz will last approximately 2 hours. Make sure you are on time or you will be at a disadvantage.

If a, b, and c are positive integers, is b = ac^(-1/2)

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50619
If a, b, and c are positive integers, is b = ac^(-1/2)  [#permalink]

Show Tags

New post 09 Oct 2017, 23:44
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

62% (01:15) correct 38% (01:13) wrong based on 207 sessions

HideShow timer Statistics

CEO
CEO
User avatar
P
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2700
Location: India
GMAT: INSIGHT
WE: Education (Education)
Reviews Badge
If a, b, and c are positive integers, is b = ac^(-1/2)  [#permalink]

Show Tags

New post Updated on: 10 Oct 2017, 05:18
Bunuel wrote:
If a, b, and c are positive integers, is \(b = \frac{a}{\sqrt{c}}\)?


(1) \(c = \frac{a^2}{b^2}\)

(2) \(\sqrt{c} = \frac{b}{a}\)


Question: is \(b = \frac{a}{\sqrt{c}}\)?

Statement 1: \(c = \frac{a^2}{b^2}\)
Taking square root both sides
√c = a/b
SUFFICIENT


Statement 2: \(\sqrt{c} = \frac{b}{a}\)
@a = b = c = 1 Answer to the question is YES
@a = 1, b=2, c = 4 Answer to the question is NO
NOT SUFFICIENT


Answer: Option A
_________________

Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION


Originally posted by GMATinsight on 10 Oct 2017, 03:43.
Last edited by GMATinsight on 10 Oct 2017, 05:18, edited 2 times in total.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50619
Re: If a, b, and c are positive integers, is b = ac^(-1/2)  [#permalink]

Show Tags

New post 10 Oct 2017, 03:46
GMATinsight wrote:
Bunuel wrote:
If a, b, and c are positive integers, is \(b = \frac{a}{c}\)?


(1) \(c = \frac{a^2}{b^2}\)

(2) \(\sqrt{c} = \frac{b}{a}\)


Question: is \(b = \frac{a}{c}\)?

Statement 1: \(c = \frac{a^2}{b^2}\)
If a = b = c = 1 then answer to the question is YES
if a = b = 2 then c = 1 then answer to the question is NO

NOT SUFFICIENT


Statement 2: \(\sqrt{c} = \frac{b}{a}\)

If a = b = c = 1 then answer to the question is YES
if a = b = 2 then c = 1 then answer to the question is NO

NOT SUFFICIENT


After combining the two statements

If a = b = c = 1 then answer to the question is YES
if a = b = 2 then c = 1 then answer to the question is NO

NOT SUFFICIENT

Answer: Option E


Sorry GMATinsight, the question is "If a, b, and c are positive integers, is \(b = \frac{a}{\sqrt{c}}\)?" NOT "If a, b, and c are positive integers, is \(b = \frac{a}{c}\)?". Edited.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Senior Manager
Senior Manager
User avatar
P
Joined: 02 Jul 2017
Posts: 293
Concentration: Entrepreneurship, Technology
GMAT 1: 730 Q50 V38
GMAT ToolKit User
Re: If a, b, and c are positive integers, is b = ac^(-1/2)  [#permalink]

Show Tags

New post 10 Oct 2017, 04:00
Bunuel wrote:
If a, b, and c are positive integers, is \(b = \frac{a}{\sqrt{c}}\)?


(1) \(c = \frac{a^2}{b^2}\)

(2) \(\sqrt{c} = \frac{b}{a}\)


(1) \(c = \frac{a^2}{b^2}\)
=> taking square root
=> \(\sqrt{c} = \frac{a}{b}\)
=> \(b = \frac{a}{\sqrt{c}}\)
Sufficient

(2) \(\sqrt{c} = \frac{b}{a}\)
=> \(b =a\sqrt{c}\)
In this case :
if c = 1 => \(b =a\sqrt{c}\) => \(b = \frac{a}{\sqrt{c}}\)
if c = 4 => \(b =a\sqrt{c}\) is not same as \(b = \frac{a}{\sqrt{c}}\)
Insufficient

Answer: A
ISB, NUS, NTU Moderator
User avatar
G
Joined: 11 Aug 2016
Posts: 312
Reviews Badge CAT Tests
Re: If a, b, and c are positive integers, is b = ac^(-1/2)  [#permalink]

Show Tags

New post 07 Jun 2018, 08:19
Bunuel wrote:
If a, b, and c are positive integers, is \(b = \frac{a}{\sqrt{c}}\)?


(1) \(c = \frac{a^2}{b^2}\)

(2) \(\sqrt{c} = \frac{b}{a}\)


Given: a,b,c are +'ve
To Calculate:\(b=\frac{a}{\sqrt{c}}\)

Statement 1:
\(c = \frac{a^2}{b^2}\)
Since, \(\sqrt{x^2}=|x|\)
and a,b,c are all +'ve [Already stated in question]
Therefore, \(\sqrt{x^2}=x\)
Using the above, we can root both sides(Since, all the variables are Positive, there will be no loss of solutions)
\(\sqrt{c}=\frac{a}{b}\)
Rearranging the terms, we get
\(b = \frac{a}{\sqrt{c}}\)
Hence Sufficient.

Statement 2:
\(\sqrt{c} = \frac{b}{a}\)
Rearranging the terms, we get:
\(b=a\sqrt{c}\)
Which is not the term we desire.
Hence Insufficient.

Answer: A

However, I do not see the need of Value Substitution while evaluating Statement 2.
Can someone throw some light on why did we do that ?
_________________

~R.
If my post was of any help to you, You can thank me in the form of Kudos!!

DS Forum Moderator
avatar
P
Joined: 21 Aug 2013
Posts: 1365
Location: India
Premium Member
Re: If a, b, and c are positive integers, is b = ac^(-1/2)  [#permalink]

Show Tags

New post 07 Jun 2018, 08:36
[quote="Rumanshu1990"][quote="Bunuel"]If a, b, and c are positive integers, is [m]b = \frac{a}{[square_root]c[/square_root]}[/m]?


(1) [m]c = [fraction]a^2/b^2[/fraction][/m]

(2) [m][square_root]c[/square_root] = [fraction]b/a[/fraction][/m][/quote]

[b]Given:[/b] a,b,c are +'ve
[b]To Calculate[/b]:[m]b=[fraction]a/[square_root]c[/square_root][/fraction][/m]

[b]Statement 1:[/b]
[m]c = [fraction]a^2/b^2[/fraction][/m]
Since, [m][square_root]x^2[/square_root]=|x|[/m]
and a,b,c are all +'ve [Already stated in question]
Therefore, [m][square_root]x^2[/square_root]=x[/m]
Using the above, we can root both sides(Since, all the variables are Positive, there will be no loss of solutions)
[m][square_root]c[/square_root]=[fraction]a/b[/fraction][/m]
Rearranging the terms, we get
[m]b = \frac{a}{[square_root]c[/square_root]}[/m]
[b]Hence Sufficient.[/b]

[b]Statement 2:[/b]
[m][square_root]c[/square_root] = [fraction]b/a[/fraction][/m]
Rearranging the terms, we get:
[m]b=a[square_root]c[/square_root][/m]
Which is not the term we desire.
[b]Hence Insufficient.[/b]

[b]Answer: A[/b]

However, I do not see the need of Value Substitution while evaluating Statement 2.
Can someone throw some light on why did we do that ?[/quote]

Hello

Value substitution is just one of the techniques which often comes in very handy while solving DS questions, especially for someone who is not so good in algebra and advanced formulas, or if one is not so good in mathematics.

Even for people who are good in formulas/algebra etc, sometimes value substitution saves time. That's why you will often see experts solving questions using this technique.

Although I agree this questions second statement can probably be very easily resolved using what you suggested.

[size=80][b][i]Posted from my mobile device[/i][/b][/size]
GMAT Club Bot
Re: If a, b, and c are positive integers, is b = ac^(-1/2) &nbs [#permalink] 07 Jun 2018, 08:36
Display posts from previous: Sort by

If a, b, and c are positive integers, is b = ac^(-1/2)

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


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.