Find all School-related info fast with the new School-Specific MBA Forum

It is currently 05 Aug 2015, 03:07
GMAT Club Tests

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

In the formula V = 1/(2r)^3, if r is halved, then V is multi

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
avatar
Joined: 10 Mar 2008
Posts: 375
Followers: 4

Kudos [?]: 103 [0], given: 0

In the formula V = 1/(2r)^3, if r is halved, then V is multi [#permalink] New post 15 Jul 2008, 11:39
2
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

71% (01:44) correct 29% (01:05) wrong based on 140 sessions
In the formula V = 1/(2r)^3, if r is halved, then V is multiplied by

A. 64
B. 8
C. 1
D. 1/8
E. 1/64
[Reveal] Spoiler: OA

Last edited by Bunuel on 21 Feb 2014, 04:10, edited 1 time in total.
Renamed the topic, edited the question and added the OA.
SVP
SVP
User avatar
Joined: 30 Apr 2008
Posts: 1889
Location: Oklahoma City
Schools: Hard Knocks
Followers: 36

Kudos [?]: 480 [0], given: 32

Re: PS: formula V= 1/(2r)^3 [#permalink] New post 15 Jul 2008, 11:42
B - about had that backwards :( :shock:

Make r = 1/2, V = 1

Make r = 1, v = 1/8
_________________

------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

GMAT Club Premium Membership - big benefits and savings

Senior Manager
Senior Manager
avatar
Joined: 07 Jan 2008
Posts: 298
Followers: 1

Kudos [?]: 27 [0], given: 0

Re: PS: formula V= 1/(2r)^3 [#permalink] New post 15 Jul 2008, 12:00
I always mess up these kinds...
Say r=2 => V1 = 1/64
when r=1; V2 = 1/8
V2 = 8*V1.
B?
SVP
SVP
User avatar
Joined: 30 Apr 2008
Posts: 1889
Location: Oklahoma City
Schools: Hard Knocks
Followers: 36

Kudos [?]: 480 [0], given: 32

Re: PS: formula V= 1/(2r)^3 [#permalink] New post 15 Jul 2008, 12:05
I totally agree with you. I mess them up to and about did this one. I saw that if I make 2r = 1, then r=1/2 so to the power of 3 doesn't matter, it's still 1/1. Then I did r =1 (double it) so then V = 1/8. So I was thinking oh, go from 1 to 1/8 multiply by 1/8...but I had worked the problem backwards. There are tricks the authors throw at us, and then there are tricks we bring to the test ourselves. We have to eliminate our own tricks. Easier said than done!

mbawaters wrote:
I always mess up these kinds...
Say r=2 => V1 = 1/64
when r=1; V2 = 1/8
V2 = 8*V1.
B?

_________________

------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

GMAT Club Premium Membership - big benefits and savings

Senior Manager
Senior Manager
avatar
Joined: 10 Mar 2008
Posts: 375
Followers: 4

Kudos [?]: 103 [0], given: 0

Re: PS: formula V= 1/(2r)^3 [#permalink] New post 15 Jul 2008, 12:09
So isnt the qtn essentially testing us on: if r is halved then what should V be multiplied by to retain the intial formula???
Senior Manager
Senior Manager
avatar
Joined: 07 Jan 2008
Posts: 298
Followers: 1

Kudos [?]: 27 [0], given: 0

Re: PS: formula V= 1/(2r)^3 [#permalink] New post 15 Jul 2008, 14:30
vksunder wrote:
So isnt the qtn essentially testing us on: if r is halved then what should V be multiplied by to retain the intial formula???

I think its asking us to reflect the changes in the value of V if r is halved!
Senior Manager
Senior Manager
User avatar
Joined: 09 Oct 2007
Posts: 467
Followers: 1

Kudos [?]: 26 [0], given: 1

Re: PS: formula V= 1/(2r)^3 [#permalink] New post 15 Jul 2008, 22:22
vksunder wrote:
So isnt the qtn essentially testing us on: if r is halved then what should V be multiplied by to retain the intial formula???


Not really, it's asking what happens to V when r is halved. In this type of problems, just pick an easy value for r and solve both equations.
Intern
Intern
avatar
Joined: 29 Jan 2014
Posts: 31
GMAT 1: 510 Q36 V26
GMAT 2: 550 Q38 V28
Followers: 0

Kudos [?]: 1 [0], given: 52

Re: In the formula V= 1/(2r)^3, if r is halved, then V is [#permalink] New post 21 Feb 2014, 02:14
Can someone solve this question with an explanation?

Thanks
_________________

Please give me Kudos if you like my post. Thank you

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 28785
Followers: 4607

Kudos [?]: 47722 [0], given: 7132

Re: In the formula V= 1/(2r)^3, if r is halved, then V is [#permalink] New post 21 Feb 2014, 04:28
Expert's post
benjamin09 wrote:
Can someone solve this question with an explanation?

Thanks


In the formula V = 1/(2r)^3, if r is halved, then V is multiplied by

A. 64
B. 8
C. 1
D. 1/8
E. 1/64

Given: \(V = \frac{1}{(2r)^3}=\frac{1}{8r^3}\)

Now, halved r is r/2, substitute r/2 instead of r: \(V' = \frac{1}{(2*\frac{r}{2})^3}=\frac{1}{r^3}\).

\(V =\frac{1}{8r^3}\) should be multiplied by 8 to get \(V'=\frac{1}{r^3}\).

Answer: B.

Or:
When r=2, then \(V = \frac{1}{(2r)^3}=\frac{1}{64}\).
When r=1, then \(V' = \frac{1}{(2r)^3}=\frac{1}{8}\).

1/64 should be multiplied by 8 to get 1/8.

Answer: B.

Similar question to practice: if-the-function-q-is-defined-by-the-formula-q-5w-4x-z-131051.html

Hope it helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis ; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) ; 12. 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?
25 extra-hard Quant Tests

GMAT Club Premium Membership - big benefits and savings

Intern
Intern
avatar
Joined: 29 Jan 2014
Posts: 31
GMAT 1: 510 Q36 V26
GMAT 2: 550 Q38 V28
Followers: 0

Kudos [?]: 1 [0], given: 52

Re: In the formula V = 1/(2r)^3, if r is halved, then V is multi [#permalink] New post 21 Feb 2014, 06:34
Thanks a lot Bunuel!
_________________

Please give me Kudos if you like my post. Thank you

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 5740
Followers: 325

Kudos [?]: 64 [0], given: 0

Premium Member
Re: In the formula V = 1/(2r)^3, if r is halved, then V is multi [#permalink] New post 07 Apr 2015, 19:28
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 Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Re: In the formula V = 1/(2r)^3, if r is halved, then V is multi   [#permalink] 07 Apr 2015, 19:28
    Similar topics Author Replies Last post
Similar
Topics:
3 Experts publish their posts in the topic For all real numbers V, the operation V* is defined by the equation V* Bunuel 4 04 Dec 2014, 06:42
1 Experts publish their posts in the topic In the figure above, the coordinates of point V are Bunuel 7 26 Aug 2012, 02:03
Experts publish their posts in the topic In the formula, V = 1/(2r)^2, if r is tripled, then V is enigma123 2 19 Feb 2012, 15:54
1 Formula for divisors study 1 16 May 2010, 00:56
37 Experts publish their posts in the topic Each digit in the two-digit number G is halved to form a new u2lover 34 08 Aug 2006, 12:49
Display posts from previous: Sort by

In the formula V = 1/(2r)^3, if r is halved, then V is multi

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.