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

It is currently 19 Aug 2018, 23:55

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

The variables a and b are non-zero integers. If a = 2b^3/c, what happe

  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: 48041
The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 00:51
2
2
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

68% (01:29) correct 32% (01:17) wrong based on 134 sessions

HideShow timer Statistics

The variables a and b are non-zero integers. If a = 2b^3/c, what happens to c when a is halved and b is doubled?

A. c is not changed.
B. c is halved.
C. c is doubled.
D. c is multiplied by 4.
E. c is multiplied by 16.

Kudos for a correct solution.

_________________

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

Manager
Manager
User avatar
Joined: 26 Dec 2011
Posts: 116
Schools: HBS '18, IIMA
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 02:31
1
1
Bunuel wrote:
The variables a and b are non-zero integers. If a = 2b^3/c, what happens to c when a is halved and b is doubled?

A. c is not changed.
B. c is halved.
C. c is doubled.
D. c is multiplied by 4.
E. c is multiplied by 16.

Kudos for a correct solution.


Solution -

Given that a = 2*b^3/c --> c = 2*b^3/a

What is the value of c when a->a/2 and b->2b.

c = 2*b^3/a = 2*(2b)^3/(a/2) = 2*2*8*b^3/a = 16*(2*b^3/a)

The value of c is 16 times the original value. ANS E.
_________________

Thanks,
Kudos Please

Current Student
avatar
S
Joined: 20 Mar 2014
Posts: 2643
Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
GMAT ToolKit User Premium Member Reviews Badge
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 03:47
Bunuel wrote:
The variables a and b are non-zero integers. If a = 2b^3/c, what happens to c when a is halved and b is doubled?

A. c is not changed.
B. c is halved.
C. c is doubled.
D. c is multiplied by 4.
E. c is multiplied by 16.

Kudos for a correct solution.


Assume a=2, b =1 000----> c = 2(1)/2 =1

Final value of c = with b =2 and a=1 ---> c = 2(2)^3/1 ---> c = 16. Thus C is multiplied by 16. E is the correct answer.
Intern
Intern
User avatar
B
Joined: 19 May 2015
Posts: 8
GMAT ToolKit User
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 04:06
1
if a is divided by 2, the whole equation is divided by two - a/2=(2b^3/c)/2 => a/2=2b^3/2c - it means that c has to be halved
if b is doubled - b^3 is multiplied by 8, which means that c also has to be multiplied by 8 to keep the equation.
hence, C is halved and than multiplied by 8, so correct answer is D - multiplied by 4.
Current Student
avatar
S
Joined: 20 Mar 2014
Posts: 2643
Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
GMAT ToolKit User Premium Member Reviews Badge
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 04:15
Tornikea wrote:
if a is divided by 2, the whole equation is divided by two - a/2=(2b^3/c)/2 => a/2=2b^3/2c - it means that c has to be halved
if b is doubled - b^3 is multiplied by 8, which means that c also has to be multiplied by 8 to keep the equation.
hence, C is halved and than multiplied by 8, so correct answer is D - multiplied by 4.


The text in red above is not correct. When you half 'a' , c gets multiplied by 2.

c=(2b^3)/(a/2) = 2* (2b^3)/a

Thus, the final effect will be to multiply c by 2 and then by 8 in effect multiplying by 16.
Senior Manager
Senior Manager
User avatar
B
Joined: 28 Jun 2015
Posts: 295
Concentration: Finance
GPA: 3.5
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 05:12
1
\(a = \frac{2b^3}{c}\), so \(c = \frac{2b^3}{a}\).

when \(a\) is halved and \(b\) is doubled, c = \(\frac{2*2(2b)^3}{a}\) = \(\frac{32b^3}{a}\).

so, \(c\) is multiplied by 16 when \(a\) is halved and \(b\) is doubled. Ans (E).
_________________

I used to think the brain was the most important organ. Then I thought, look what’s telling me that.

Intern
Intern
avatar
Joined: 21 Jul 2015
Posts: 2
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 08:12
1
When a = 2 and b = 2 ; C = 8
a*.5 = 1
b *2 = 4

When a = 1 and b = 4 ; C = 128

8x = 128
x = 16
Intern
Intern
avatar
Joined: 08 Jun 2015
Posts: 3
GPA: 3.9
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 10:48
1
rearrange equation so that you have c=(2b^3)/a

a=2 b=1
c=1

a=1 b=2
c=16

Answer: E
_________________

GMATPrep1=>720
GMATPrep2=>760

Intern
Intern
User avatar
Joined: 08 Jul 2012
Posts: 49
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 24 Jul 2015, 10:56
1
Bunuel wrote:
The variables a and b are non-zero integers. If a = 2b^3/c, what happens to c when a is halved and b is doubled?

A. c is not changed.
B. c is halved.
C. c is doubled.
D. c is multiplied by 4.
E. c is multiplied by 16.

Kudos for a correct solution.


a=2b^3/c

c=2b^3/a

when a is halved and b is doubled

c=2(2b)^3/(a/2)
c=16*2b^3/a

Ans. E c is multiplied by 16.
_________________

Our greatest weakness lies in giving up. The most certain way to succeed is always to try just one more time. - Thomas A. Edison

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 48041
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 26 Jul 2015, 12:20
Bunuel wrote:
The variables a and b are non-zero integers. If a = 2b^3/c, what happens to c when a is halved and b is doubled?

A. c is not changed.
B. c is halved.
C. c is doubled.
D. c is multiplied by 4.
E. c is multiplied by 16.

Kudos for a correct solution.


800score Official Solution:

The easiest way to solve this problem is to plug in numbers for the variables and then backsolve for c. Use even numbers, because even numbers can be halved without leaving fractions.

Let b = 2 and c = 4. Solve the equation:
a = (2(2³))/4 = 16/4 = 4.
So, a = 4 when b = 2 and c = 4.

Now halve a and double b: a = 2, b = 4. Plug these values into the equation and see what happens to c:
2 = ((2(4³))/c
2 = (2(64))/c
2 = 128/c
2c = 128
c = 64.

Comparing this to the original value of c, which was 4, we see that the new value for c is 16 times the original value.

Another way to attack this problem is to solve for c to arrive at the same answer.

The correct answer is choice (E).
_________________

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

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 7773
Premium Member
Re: The variables a and b are non-zero integers. If a = 2b^3/c, what happe  [#permalink]

Show Tags

New post 16 Jul 2018, 07:34
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: The variables a and b are non-zero integers. If a = 2b^3/c, what happe &nbs [#permalink] 16 Jul 2018, 07:34
Display posts from previous: Sort by

The variables a and b are non-zero integers. If a = 2b^3/c, what happe

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

Events & Promotions

PREV
NEXT


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®.