NEW HERE? LEARN MORE
closeclose
Last visit was: 25 Apr 2024, 03:57 It is currently 25 Apr 2024, 03:57
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

Consider ab = c, where a > 0, b > 0, and c is a positive constant. If

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92912
Own Kudos [?]: 618904 [3]
Given Kudos: 81595
Send PM
CAT Tests Forum Quiz Mode
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   23 Apr 2018, 23:57
3
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

35% (medium)

Question Stats:

66% (01:39) correct 34% (01:32) wrong based on 168 sessions
Hide Show timer Statistics
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If b increases by 50%, then what percent change in a should occur, so that the equation remains true?

(A) 25% decrease
(B) 33 1/3% decrease
(C) 25% increase
(D) 50% increase
(E) 66 2/3% increase
ShowHide Answer
Official Answer
B
User avatar
P
DavidTutorexamPAL
examPAL Representative
Joined: 07 Dec 2017
Posts: 1050
Own Kudos [?]: 1777 [1]
Given Kudos: 26
Send PM
Re: Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   24 Apr 2018, 00:30
1
Bookmarks
Bunuel wrote:
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If b increases by 50%, then what percent change in a should occur, so that the equation remains true?

(A) 25% decrease
(B) 33 1/3% decrease
(C) 25% increase
(D) 50% increase
(E) 66 2/3% increase


We'll write out what we're told as expressions so we understand what our given data is.
This is a Precise approach.

Saying that b increases by 50% is like saying that it is multiplied by 1.5.
So, we need to divide a by 1.5 so that their ratio remains constant.
That is, we need to multiply it by 1/1.5 = 2/3. This is the same as decreasing it by 33 1/3%.

(B) is our answer.
User avatar
S
Tulkin987
Manager
Manager
Joined: 28 Nov 2017
Posts: 113
Own Kudos [?]: 147 [0]
Given Kudos: 135
Location: Uzbekistan
Send PM
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   Updated on: 24 Apr 2018, 00:32
Bunuel wrote:
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If b increases by 50%, then what percent change in a should occur, so that the equation remains true?

(A) 25% decrease
(B) 33 1/3% decrease
(C) 25% increase
(D) 50% increase
(E) 66 2/3% increase


\((a*x)*(1.5*b)=1*c\)
\(1.5*x=1\)
\(x=\frac{2}{3}\) --> \(33\frac{1}{3}\)% decrease from \(1\)(or \(100\)%)

Answer: B

Originally posted by Tulkin987 on 24 Apr 2018, 00:31.
Last edited by Tulkin987 on 24 Apr 2018, 00:32, edited 1 time in total.
User avatar
B
praveenbaranwal
Intern
Intern
Joined: 18 Feb 2018
Posts: 9
Own Kudos [?]: 53 [0]
Given Kudos: 7
Location: New Zealand
Concentration: Strategy, Technology
WE:Consulting (Computer Software)
Send PM
GMAT ToolKit User
Re: Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   24 Apr 2018, 00:31
Option B
ab = c, where a > 0, b > 0, and c is a positive constant.

After increase of "b" by 50%, the new value of "b" = "1.5b"
To compensate the change in "b", the new value of "a"= a/1.5=a*2/3
Therefore change in "a" = a=2/3a= 1/3a =33 1/3 %
User avatar
P
push12345
Director
Director
Joined: 02 Oct 2017
Posts: 552
Own Kudos [?]: 481 [0]
Given Kudos: 14
Send PM
Re: Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   11 May 2018, 05:00
Ab=c
If b increase by 50 percent then b becomes (3b/2)

To keep equation same a has to become 2a/3
Means a has to reduce from 100 percent- a
To 2a/3 i.e. 66.66 percent

So change in percent=100-66.66=33.33

Posted from my mobile device
User avatar
L
ScottTargetTestPrep
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 18756
Own Kudos [?]: 22050 [0]
Given Kudos: 283
Location: United States (CA)
Send PM
Re: Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   14 May 2018, 16:45
Expert Reply
Bunuel wrote:
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If b increases by 50%, then what percent change in a should occur, so that the equation remains true?

(A) 25% decrease
(B) 33 1/3% decrease
(C) 25% increase
(D) 50% increase
(E) 66 2/3% increase



We can let k be a constant such that

(ka)(1.5b) = c

(3/2)k(ab) = c

Since ab = c, so we want:

(3/2)k = 1

k = 2/3

We see that we need to multiply a by 2/3, i.e., decrease a by 1/3 = 33 ⅓% of its value, in order for the equation to remain true..

Answer: B
User avatar
L
generis
Senior SC Moderator
Joined: 22 May 2016
Posts: 5330
Own Kudos [?]: 35487 [1]
Given Kudos: 9464
Send PM
CAT Tests
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   14 May 2018, 20:19
1
Kudos
Expert Reply
Bunuel wrote:
Consider ab = c, where a > 0, b > 0, and c is a positive constant. If b increases by 50%, then what percent change in a should occur, so that the equation remains true?

(A) 25% decrease
(B) 33 1/3% decrease
(C) 25% increase
(D) 50% increase
(E) 66 2/3% increase

Assign values
The integers 120 and 60 often work well for percent increase and decrease problems.

\(a = 6\)
\(b = 10\)
\(c = 60\)
\((a*b)= c\)
\((6*10) = 60\)

\(b\) increases by 50%:
\(b_2=10*1.5=15\)
\(c=60\) is constant

What must \(a\) become?
\(a_2*b_2=c\)
\(a_2*15=60\)
\(a_2=4\)

Percent decrease? \(\frac{New-Old}{Old}*100\)
Percent decrease:\((\frac{6-4}{6})=\frac{2}{6}=\\
(\frac{1}{3}*100)=(.33*100)=33\frac{1}{3}\) %

Answer B

Inverse proportion: flip the fraction
If the product of two variables is constant, percent increase and percent decrease are inversely proportional.

1) Find the fraction for the percent change of the factor (\(b\)) that increases:
50% increase = \(1.5=1\frac{1}{2}=\frac{3}{2}\)
2) Flip that fraction. \(\frac{3}{2}\)=>\(\frac{2}{3}\)
3) subtract from 1. That's the other factor's percent decrease: \(1 - \frac{2}{3}=\frac{1}{3}*100=33\frac{1}{3}\)%
Or, \(a\) is now \(\frac{2}{3}\) of what it was, which is a 33.3% decrease

Answer B
avatar
B
Likhitha30chowdary
Intern
Intern
Joined: 25 Feb 2018
Posts: 8
Own Kudos [?]: 0 [0]
Given Kudos: 42
Send PM
Re: Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink] New post   24 May 2018, 05:49
ab=c
new value of b is 1.5b
new a * 1.5 b =a *b
new a = a*2/3
2/3 => 33.3%
therefore, a should decrease by 33.3%
GMAT Club Bot
gmatclubot
Re: Consider ab = c, where a > 0, b > 0, and c is a positive constant. If [#permalink]
24 May 2018, 05:49
Moderators:
Bunuel
Math Expert
92912 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions