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

It is currently 17 Oct 2019, 11:00

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

Which of the following is equivalent to 21/6 ?

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58402
Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 06 Jun 2017, 10:01
1
10
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

60% (01:19) correct 40% (01:32) wrong based on 292 sessions

HideShow timer Statistics

Senior PS Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 3335
Location: India
GPA: 3.12
Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 06 Jun 2017, 10:25
1
1
\(\frac{\sqrt{21}}{6}\) = \(\frac{\sqrt{7*3}}{6}\)

= \(\frac{\sqrt{7*3}}{\sqrt{36}}\)

= \(\frac{\sqrt{7*3}}{\sqrt{12*3}}\) = \(\sqrt{\frac{7}{12}}\) (Option D)
_________________
You've got what it takes, but it will take everything you've got
GMAT Club Legend
GMAT Club Legend
User avatar
V
Joined: 12 Sep 2015
Posts: 4007
Location: Canada
Re: Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 06 Jun 2017, 11:08
Top Contributor
Bunuel wrote:
Which of the following is equivalent to \(\frac{\sqrt{21}}{6}\)?

A. \(\frac{\sqrt{7}}{2}\)

B. 7/12

C. \(\sqrt{\frac{7}{2}}\)

D. \(\sqrt{\frac{7}{12}}\)

E. \(\frac{7\sqrt{3}}{2}\)


Useful rule: \(\frac{\sqrt{x}}{\sqrt{y}} = {\sqrt{\frac{x}{y}}}\)

So, \(\frac{\sqrt{21}}{6} =\frac{\sqrt{21}}{\sqrt{36}} = {\sqrt{\frac{21}{36}}} = {\sqrt{\frac{7}{12}}}\)

Answer:
_________________
Test confidently with gmatprepnow.com
Image
Current Student
User avatar
B
Joined: 06 Sep 2016
Posts: 125
Location: Italy
Schools: EDHEC (A$)
GMAT 1: 650 Q43 V37
GPA: 3.2
WE: General Management (Human Resources)
Re: Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 27 Jun 2017, 02:41
Why in this case it's wrong to square all and remove the square root?
In this question https://gmatclub.com/forum/2-240047.html I saw that it's feasible... why in this case it isn't?
Senior PS Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 3335
Location: India
GPA: 3.12
Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 27 Jun 2017, 03:34
MvArrow wrote:
Why in this case it's wrong to square all and remove the square root?
In this question https://gmatclub.com/forum/2-240047.html I saw that it's feasible... why in this case it isn't?



Let a= \(\frac{\sqrt{21}}{6}\)

If you want to remove the square root, square both sides

\(a^2 =\frac{21}{6^2}\) = \(\frac{21}{36} = \frac{7*3}{12*3} = \frac{7}{12}\)

Taking square root, we get a = \(\sqrt{\frac{7}{12}}\)(Option D)
Hope it helps!
_________________
You've got what it takes, but it will take everything you've got
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58402
Re: Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 27 Jun 2017, 03:35
1
MvArrow wrote:
Which of the following is equivalent to \(\frac{\sqrt{21}}{6}\)?

A. \(\frac{\sqrt{7}}{2}\)

B. 7/12

C. \(\sqrt{\frac{7}{2}}\)

D. \(\sqrt{\frac{7}{12}}\)

E. \(\frac{7\sqrt{3}}{2}\)

Why in this case it's wrong to square all and remove the square root?
In this question https://gmatclub.com/forum/2-240047.html I saw that it's feasible... why in this case it isn't?


You can do this way but you should square the options too to compare apples with apples. When you square, the question becomes: which of the following is equivalent to \((\frac{\sqrt{21}}{6})^2=\frac{21}{36}=\frac{7}{12}\). Option D squared gives exactly this value: \((\sqrt{\frac{7}{12}})^2=\frac{7}{12}\)

Answer: D.

Hope it helps.
_________________
Director
Director
User avatar
D
Affiliations: IIT Dhanbad
Joined: 13 Mar 2017
Posts: 728
Location: India
Concentration: General Management, Entrepreneurship
GPA: 3.8
WE: Engineering (Energy and Utilities)
Re: Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 27 Jun 2017, 03:55
Bunuel wrote:
Which of the following is equivalent to \(\frac{\sqrt{21}}{6}\)?

A. \(\frac{\sqrt{7}}{2}\)

B. 7/12

C. \(\sqrt{\frac{7}{2}}\)

D. \(\sqrt{\frac{7}{12}}\)

E. \(\frac{7\sqrt{3}}{2}\)


\(\frac{\sqrt{21}}{6}\)
\(\frac{\sqrt{7*3}}{\sqrt{3*3*2*2}}\)
\(\frac{\sqrt{7}}{\sqrt{3*2*2}}\)
\(\frac{\sqrt{7}}{\sqrt{12}}\)

Answer D.
_________________
CAT 2017 (98.95) & 2018 (98.91) : 99th percentiler
UPSC Aspirants : Get my app UPSC Important News Reader from Play store.

MBA Social Network : WebMaggu


Appreciate by Clicking +1 Kudos ( Lets be more generous friends.)



What I believe is : "Nothing is Impossible, Even Impossible says I'm Possible" : "Stay Hungry, Stay Foolish".
Current Student
User avatar
B
Joined: 06 Sep 2016
Posts: 125
Location: Italy
Schools: EDHEC (A$)
GMAT 1: 650 Q43 V37
GPA: 3.2
WE: General Management (Human Resources)
Re: Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 27 Jun 2017, 04:16
Bunuel wrote:
MvArrow wrote:
Which of the following is equivalent to \(\frac{\sqrt{21}}{6}\)?

A. \(\frac{\sqrt{7}}{2}\)

B. 7/12

C. \(\sqrt{\frac{7}{2}}\)

D. \(\sqrt{\frac{7}{12}}\)

E. \(\frac{7\sqrt{3}}{2}\)

Why in this case it's wrong to square all and remove the square root?
In this question https://gmatclub.com/forum/2-240047.html I saw that it's feasible... why in this case it isn't?


You can do this way but you should square the options too to compare apples with apples. When you square, the question becomes: which of the following is equivalent to \((\frac{\sqrt{21}}{6})^2=\frac{21}{36}=\frac{7}{12}\). Option D squared gives exactly this value: \((\sqrt{\frac{7}{12}})^2=\frac{7}{12}\)

Answer: D.

Hope it helps.


Great! Thanks! I din't think about it
:oops:
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 13242
Re: Which of the following is equivalent to 21/6 ?  [#permalink]

Show Tags

New post 24 Feb 2019, 09:01
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Bot
Re: Which of the following is equivalent to 21/6 ?   [#permalink] 24 Feb 2019, 09:01
Display posts from previous: Sort by

Which of the following is equivalent to 21/6 ?

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





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