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

It is currently 23 Sep 2014, 14:28

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

Power rules question

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 15 Sep 2011
Posts: 4
Followers: 0

Kudos [?]: 0 [0], given: 2

Power rules question [#permalink] New post 15 Oct 2011, 11:26
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

89% (01:57) correct 11% (02:19) wrong based on 9 sessions
Hello,

can anybody help me understand this question?

Many thanks!!
Daniele


If 2^x- 2^(x-2) = 3(2^13) then x is equal to ?
a .9
b.11
c.13
d.15
e.17
[Reveal] Spoiler: OA
Manager
Manager
avatar
Joined: 21 Aug 2010
Posts: 93
Location: United States
Followers: 1

Kudos [?]: 25 [0], given: 80

GMAT ToolKit User CAT Tests
Re: Power rules question [#permalink] New post 15 Oct 2011, 12:43
danielezunino wrote:
Hello,

can anybody help me understand this question?

Many thanks!!
Daniele


If 2^x- 2^(x-2) = 3(2^13) then x is equal to ?
a .9
b.11
c.13
d.15
e.17



Q:2^x- 2^(x-2) = 3(2^13)


==>2^x = 3(2^13)+2^(x-2)

So the value of X should be more than 13. Only 2 options which are greater than 13.

15 and 17

If we substitute 15.

2^15 = 3(2^13)+2^13
2^2 * 2^13 = 4(2^13)
4(2^13) = 4 (2^13) so 15 (D )
_________________

-------------------------------------

3 KUDOS received
Manager
Manager
avatar
Joined: 21 Aug 2010
Posts: 93
Location: United States
Followers: 1

Kudos [?]: 25 [3] , given: 80

GMAT ToolKit User CAT Tests
Re: Power rules question [#permalink] New post 15 Oct 2011, 12:52
3
This post received
KUDOS
gopu106 wrote:
danielezunino wrote:
Hello,

can anybody help me understand this question?

Many thanks!!
Daniele


If 2^x- 2^(x-2) = 3(2^13) then x is equal to ?
a .9
b.11
c.13
d.15
e.17



Q:2^x- 2^(x-2) = 3(2^13)


==>2^x = 3(2^13)+2^(x-2)

So the value of X should be more than 13. Only 2 options which are greater than 13.

15 and 17

If we substitute 15.

2^15 = 3(2^13)+2^13
2^2 * 2^13 = 4(2^13)
4(2^13) = 4 (2^13) so 15 (D )


Another way

Q:2^x- 2^(x-2) = 3(2^13)

==>[2^2 * 2^(x-2)] - 2^(x-2) = 3(2^13)
==>4[2^(x-2)] - 2^(x-2) = 3(2^13)
==>3[2^(x-2)] = 3(2^13)

==>x-2 = 13
x=15 (D)
_________________

-------------------------------------

3 KUDOS received
Manager
Manager
avatar
Status: MBA Aspirant
Joined: 12 Jun 2010
Posts: 178
Location: India
Concentration: Finance, International Business
WE: Information Technology (Investment Banking)
Followers: 3

Kudos [?]: 21 [3] , given: 1

GMAT Tests User
Re: Power rules question [#permalink] New post 15 Oct 2011, 22:35
3
This post received
KUDOS
Let us take 2^x =a

now in the equation we replace 2^x by a
=> a-a/4 = 3(2^13)
=>a/4=2^13
=>a=2^15

now a=2^x =>2^x = 2^15

so x=15
Intern
Intern
avatar
Joined: 15 Sep 2011
Posts: 4
Followers: 0

Kudos [?]: 0 [0], given: 2

Re: Power rules question [#permalink] New post 16 Oct 2011, 00:13
Thanks a lot to both of you!!! now it is really clear :-D
Re: Power rules question   [#permalink] 16 Oct 2011, 00:13
    Similar topics Author Replies Last post
Similar
Topics:
Rule of three - Conceptual question danzig 1 17 Dec 2012, 14:20
Experts publish their posts in the topic General Math Rule Question DJK 2 10 Jan 2012, 17:01
1 Root rule question leadout1 3 16 Aug 2011, 14:36
1 Power Question KusumChanrai 2 25 Oct 2009, 06:16
Power Prep Question jeremy02 2 03 Oct 2004, 21:29
Display posts from previous: Sort by

Power rules question

  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®.