It is currently 20 Oct 2017, 05:39

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Exponents and Roots

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 19 Oct 2011
Posts: 6

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

Exponents and Roots [#permalink]

Show Tags

New post 28 Oct 2011, 03:35
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 2 sessions

HideShow timer Statistics

Simplify the following fraction:

2^21/4^4(4^5-4^3)

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

Intern
Intern
avatar
Joined: 19 Oct 2011
Posts: 6

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

Re: Exponents and Roots [#permalink]

Show Tags

New post 28 Oct 2011, 05:12
answer is supposed to be: 2^7/15?!

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

Intern
Intern
avatar
Joined: 19 Oct 2011
Posts: 6

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

Re: Exponents and Roots [#permalink]

Show Tags

New post 28 Oct 2011, 10:55
Can anybody explain the way of calculation? That would be really great!

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

Manager
Manager
User avatar
Status: livin on a prayer!!
Joined: 12 May 2011
Posts: 120

Kudos [?]: 34 [0], given: 1

Location: Australia
Re: Exponents and Roots [#permalink]

Show Tags

New post 28 Oct 2011, 16:27
Hi Corinna,

Here is my working out.

First, let's simplify the bottom expression.

4^4 (4^5 -4^3)

Expand

4^9 - 4^7

Take out common factor

4^7 (4^2 - 1)

= 4^7 (15)

Turn the 4 into a base of 2, which is 2^2

So (2^2)^7 ( 15)

= 2^14 (15)

Now we can cancel out the 2^14 by the 2^21 on the top so the top becomes 2^7

So the answer is

2^7/15

I hope that makes sense.
_________________

Aim for the sky! (800 in this case)
If you like my post, please give me Kudos :)

Kudos [?]: 34 [0], given: 1

Current Student
avatar
Joined: 08 Jan 2009
Posts: 323

Kudos [?]: 158 [0], given: 7

GMAT 1: 770 Q50 V46
Re: Exponents and Roots [#permalink]

Show Tags

New post 28 Oct 2011, 18:28
This question is a bit silly without answer choices as it's not clear when the simplification is finished, but anyways:

\(\frac{2^{21}}{4^4*(4^5-4^3)}\)

\(\frac{2^{21}}{2^8*(2^{10}-2^6)}\)

\(\frac{2^{21}}{2^{14}*(2^4-1)}\)

\(\frac{2^{7}}{2^4-1}\)

\(\frac{2^{7}}{15}\)

\(\frac{128}{15}\)

Kudos [?]: 158 [0], given: 7

Re: Exponents and Roots   [#permalink] 28 Oct 2011, 18:28
Display posts from previous: Sort by

Exponents and Roots

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


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®.