GMAT Changed on April 16th - Read about the latest changes here
close

It is currently 26 Apr 2018, 23:50
Search
Register
GMAT Club Tests
Decision Tracker
My Rewards
New posts
Unanswered

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 Workbook Learn more
Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar
CLICK HERE TO HIDE/SHOW EVENTS

If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
  Sort by Date Sort by Kudos  
Search for:
 
Print view
First unread post
Author Message
TAGS:

Hide Tags
2 KUDOS received
Director
Director
User avatar
Status: No dream is too large, no dreamer is too small
Joined: 14 Jul 2010
Posts: 556
If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 01 May 2011, 07:42
2
This post received
KUDOS
9
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  85% (hard)

Question Stats:

43% (01:16) correct 57% (00:55) wrong based on 323 sessions

HideShow timer Statistics

If 3^a * 4^b = c, what is the value of b?

(1) 5^a = 25
(2) c = 36

OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/if-3-a-4-b-c ... 06047.html
[Reveal] Spoiler: OA

_________________

Collections:-
PSof OG solved by GC members: http://gmatclub.com/forum/collection-ps-with-solution-from-gmatclub-110005.html
DS of OG solved by GC members: http://gmatclub.com/forum/collection-ds-with-solution-from-gmatclub-110004.html
100 GMAT PREP Quantitative collection http://gmatclub.com/forum/gmat-prep-problem-collections-114358.html
Collections of work/rate problems with solutions http://gmatclub.com/forum/collections-of-work-rate-problem-with-solutions-118919.html
Mixture problems in a file with best solutions: http://gmatclub.com/forum/mixture-problems-with-best-and-easy-solutions-all-together-124644.html

VP
VP
avatar
Status: There is always something new !!
Affiliations: PMI,QAI Global,eXampleCG
Joined: 08 May 2009
Posts: 1153
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 02 May 2011, 04:45
straight B. 36 = 2 ^2 * 3^2
_________________

Visit -- http://www.sustainable-sphere.com/
Promote Green Business,Sustainable Living and Green Earth !!

Manager
Manager
avatar
Joined: 10 Jul 2010
Posts: 181
Reviews Badge
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 09 Nov 2011, 08:52
I'm going to go with B

36 = \(3^2 and 2^2\)

you are given that \(3^a*4^b=c\)

we can break down 4 to 2^2b
So now we have

\(3^a*2^2b=2^2*3^2\)

so a= 2, b = 2
1 KUDOS received
Intern
Intern
avatar
Joined: 07 Oct 2011
Posts: 30
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 09 Nov 2011, 09:41
1
This post received
KUDOS
a and b are not integers here.

consider this:

Now for every value of a, there is a different value of b.
Say, a = 1, then 4^b = 12 and b = 1.79 approx
a = 2, then 4^b = 4 and b = 1
a = 3, then 4^b = 36/27 and b = 0.2 approx

so answer is C
2 KUDOS received
Intern
Intern
avatar
Status: Stay Hungry, Stay Foolish.
Joined: 05 Sep 2011
Posts: 36
Location: India
Concentration: Marketing, Social Entrepreneurship
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 13 Nov 2011, 09:20
2
This post received
KUDOS
The question does not mention a and b to be Integers.
Individually,none of the statements suffice to reach the value of b.

Both the statements when used together,give the value of b.
3^2 * 4^b = 36.
b=1

Hence C.
Expert Post
4 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 44657
Premium Member CAT Tests
Top Member of the Month
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 04 Feb 2012, 15:50
4
This post received
KUDOS
Expert's post
7
This post was
BOOKMARKED
amit2k9 wrote:
straight B. 36 = 2 ^2 * 3^2


If 3^a*4^b = c, what is the value of b?

Note that we are not told that the variables are integers only.

(1) 5^a = 25 --> \(a=2\), but we can not get the values of \(b\). Not sufficient.

(2) c = 36 --> \(3^a*4^b = c\): it's tempting to write \(3^2*4^1=36\) and say that \(b=1\) but again we are not told that the variables are integers only. So, for example it can be that \(3^a=36\) for some non-integer \(a\) and \(b=0\), making \(4^b\) equal to 1 --> \(3^a*4^b =36*1=36\). Not sufficient.

(1)+(2) As \(a=2\) and \(c = 36\) then \(9*4^b=36\) --> \(b=1\). Sufficient.

Answer: C.

Hope it's clear.
_________________

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

Intern
Intern
avatar
Joined: 21 Feb 2013
Posts: 8
Schools: Arizona State"19
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 19 Jun 2015, 08:15
Hi Bunnel in the above explantion how can 3^a=36 be possible for any value a, it has to have an even no. plz clarify my doubt
Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 44657
Premium Member CAT Tests
Top Member of the Month
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 19 Jun 2015, 08:21
Expert's post
caster88 wrote:
Hi Bunnel in the above explantion how can 3^a=36 be possible for any value a, it has to have an even no. plz clarify my doubt


We are NOT told that a and b are integers. So, there exists some irrational a for which 3^a = 36: \(a= \frac{2 (log(2)+log(3))}{log(3)}\approx{3.2619}\)
_________________

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

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 44657
Premium Member CAT Tests
Top Member of the Month
Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c [#permalink]

Show Tags

New post 30 Dec 2017, 00:09
Expert's post
Baten80 wrote:
If 3^a * 4^b = c, what is the value of b?

(1) 5^a = 25
(2) c = 36



OPEN DISCUSSION OF THIS QUESTION IS HERE: https://gmatclub.com/forum/if-3-a-4-b-c ... 06047.html
_________________

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

Re: If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c   [#permalink] 30 Dec 2017, 00:09
Print view
First unread post
Display posts from previous: Sort by

If 3^a * 4^b = c, what is the value of b? (1) 5^a = 25 (2) c

  post reply Question banks Downloads My Bookmarks Reviews Important topics  

Moderators: chetan2u, VeritasPrepKarishma, Bunuel, mikemcgarry, amanvermagmat, gmatbusters

Search for:


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

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions