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

It is currently 23 Oct 2014, 03:20

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

can someone tell me the shortcut for this silly problem?

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 20 Jun 2007
Posts: 13
Followers: 0

Kudos [?]: 3 [0], given: 0

can someone tell me the shortcut for this silly problem? [#permalink] New post 04 Jul 2007, 14:19
can someone tell me the shortcut for this silly problem?

(5^21) x (4^11) = (2 x 10^n) , what is the value of n?

thanks :)
Intern
Intern
avatar
Joined: 03 Jul 2007
Posts: 8
Followers: 0

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

 [#permalink] New post 04 Jul 2007, 15:11
no shortcut, but may be it helps?

5^11*5^10*4^11=2*10^n
(5*4)^11 * 5^10 =
20^10*20*5^10 =
100^10 * 20 = 2 * 10^n | :2
10^10*10^10 * 10 = 10^n
10^21 = 10^n

cya
Mazar
Manager
Manager
avatar
Joined: 11 Mar 2007
Posts: 69
Followers: 1

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

 [#permalink] New post 04 Jul 2007, 17:09
I would do it a slightyly different way:

(5^21)*(4^11)=2*10^n
(5^21)*(2^22)=2*10^n
(5^21)*(2)(2^21)=2*10^n
2*(5^21)*(2^21)=2*10^n
2*10^21...
1 KUDOS received
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 07 Jul 2004
Posts: 5095
Location: Singapore
Followers: 19

Kudos [?]: 155 [1] , given: 0

 [#permalink] New post 04 Jul 2007, 17:45
1
This post received
KUDOS
5^21 * 2^22 = 5^21 * 2^21 * 2 = 10^21 * 2

so n = 21
Director
Director
avatar
Joined: 09 Aug 2006
Posts: 767
Followers: 1

Kudos [?]: 52 [0], given: 0

Re: (5^21) x (4^11) = (2 x 10^n) [#permalink] New post 04 Jul 2007, 23:45
dzelkas wrote:
can someone tell me the shortcut for this silly problem?

(5^21) x (4^11) = (2 x 10^n) , what is the value of n?

thanks :)


(5^21)(2^22)=2*(2*5)^n
(5^21)(2^22)=2*2^n*5^n
(5^21)(2^22)=2^n+1*5*n
Equate either term to solve for n

5^21=5^n => n=21
or
2^22=2^n+1 => n=21
Senior Manager
Senior Manager
User avatar
Joined: 24 Nov 2006
Posts: 351
Followers: 1

Kudos [?]: 11 [0], given: 0

Re: (5^21) x (4^11) = (2 x 10^n) [#permalink] New post 05 Jul 2007, 20:55
dzelkas wrote:
can someone tell me the shortcut for this silly problem?

(5^21) x (4^11) = (2 x 10^n) , what is the value of n?

thanks :)


Start with this fact: 4 = 2^2

From the expression: 5^21 * (2^2)^11 = 5^21 * 2^22

Now, include this fact: 10 = 5*2

(5*2)^21 * 2 = 10^21 * 2

Therefore, n = ???

Yep, 21.
Senior Manager
Senior Manager
avatar
Joined: 11 Jun 2006
Posts: 254
Followers: 3

Kudos [?]: 4 [0], given: 0

 [#permalink] New post 05 Jul 2007, 21:24
Shortcut:

Since you know that there is a 5^21 on the left side. You know that for the equation to be equal, there needs to be exactly 21 5's on the right side. The only way to create 21 5's is to have n=21.
  [#permalink] 05 Jul 2007, 21:24
    Similar topics Author Replies Last post
Similar
Topics:
24 Can someone tell me the formula of consecutive sum? mandb 13 14 Oct 2009, 13:51
1 Experts publish their posts in the topic Can someone explain this problem to me? benbo1234 8 15 Mar 2009, 18:53
Can someone tell me if this is correct? This statement was bmwhype2 5 31 Jul 2007, 04:01
can someone pls tell me the formula for velocity of sushom101 1 19 Oct 2005, 22:31
Display posts from previous: Sort by

can someone tell me the shortcut for this silly problem?

  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®.