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

It is currently 25 Oct 2014, 19:02

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

Ratio of code words

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 06 May 2009
Posts: 78
Followers: 2

Kudos [?]: 12 [0], given: 3

Ratio of code words [#permalink] New post 09 Jul 2009, 01:08
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

100% (01:02) correct 0% (00:00) wrong based on 0 sessions
If a code word is defined to be a sequence of different letters chosen from the 10 letters A, B, C, D, E, F, G, H, I, and J, what is the ratio of the number of 5-letter code words to the number of 4-letter code words?
A. 5 to 4
B. 3 to 2
C. 2 to 1
D. 5 to 1
E. 6 to 1
Senior Manager
Senior Manager
avatar
Joined: 25 Mar 2009
Posts: 305
Followers: 6

Kudos [?]: 72 [0], given: 6

Re: Ratio of code words [#permalink] New post 09 Jul 2009, 08:19
I’m not too good at these, but I’ll give it a shot. The wording of the question seems like order should not matter, but I tried solving that way and it didn't work. In this case ORDER MATTERS. I am unable to articulate why. Someone please explain for all of our edification.

Method #1: Using the permutation formula
# of 5 letter code words:
nPr = n! / (n – r)! = 10! / (10 – 5)! = 10*9*8*7*6

# of 4 letter code words:
nPr = 10! / (10 – 4)! = 10*9*8*7

# of 5 words / # of 4 words = (10*9*8*7*6)/(10*9*8*7) = 6 = 6/1

Answer is E.

Method #2: Using the “slots” method

# of 5 letter code words:
There are 5 empty slots below. For the first slot, you have an option of choosing 10 different letters. So fill that slot in with 10. For the second slot, you now have 9 letters to choose from. For the third slot, you have 8 letters. Keep going until you fill in all the slots and multiply all the numbers. That gives you the total # of possibilities.
__ __ __ __ __

10 * 9 * 8 * 7 * 6

# of 4 letter code words:
__ __ __ __

10 * 9 * 8 * 7

Ratio = (10*9*8*7*6)/(10*9*8*7) = 6 = 6/1

Answer E.
Re: Ratio of code words   [#permalink] 09 Jul 2009, 08:19
    Similar topics Author Replies Last post
Similar
Topics:
If a code word is defined to be a sequence of different tarek99 4 14 Apr 2008, 12:09
If a code word is defined to be a sequence of different marcodonzelli 3 19 Jan 2008, 05:09
If a code word is defined to be a sequence of different gmatornot 4 23 Aug 2006, 19:36
If a code word is defined to be a sequence of different GMATCUBS21 6 23 Jun 2006, 14:35
If a code word is defined to be a sequence of different M8 3 25 Apr 2006, 11:21
Display posts from previous: Sort by

Ratio of code words

  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®.