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

 It is currently 12 Mar 2014, 23:13

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# telephone extensions

Author Message
TAGS:
Director
Joined: 25 Oct 2008
Posts: 612
Location: Kolkata,India
Followers: 8

Kudos [?]: 114 [0], given: 100

telephone extensions [#permalink]  08 Jun 2009, 05:13
00:00

Difficulty:

5% (low)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
If all of the telephone extensions in a certain company must be even numbers, and if each of the extensions uses all four of the digits 1, 2, 3, and 6, what is the greatest number of four-digit extensions that the company can have?

(A) 4 (B) 6 (C) 12

(D) 16 (E) 24

[spoiler]OA:(c)[/spoiler]

The wording of the problem itself is not clear.I could'nt figure out what we are supposed to find in the first place?Nevertheless I answered 4!=24 which is wrong.Can someone please shed some light?
_________________
Intern
Joined: 28 Feb 2009
Posts: 28
Followers: 0

Kudos [?]: 1 [1] , given: 8

Re: telephone extensions [#permalink]  08 Jun 2009, 12:24
1
KUDOS
it should be 12 ---

digit 1 * digit 2 * digit 3 * digit 4

digit 4 -- last digit is having 2 option only even.
digit 3 -- left out 3
digit 2 has left out 2
digit 1 has left out 1.

multiply all ways u get 1*2*3*2 = 12....

Current Student
Joined: 03 Aug 2006
Posts: 117
Followers: 4

Kudos [?]: 88 [1] , given: 3

Re: telephone extensions [#permalink]  09 Jun 2009, 15:04
1
KUDOS

You are on the right track..the total number of permutations is 4! = 24

However there is a restriction that all extensions should be even i.e. the last digit of each extension should be an even number i.e. the last digit should be either 2 or 6. As there are 2 even digits and two odd digits. Half of the permutations should be even and the remaining odd.

Divide 24/2 results into 12
Intern
Joined: 27 Apr 2009
Posts: 12
Followers: 0

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

Re: telephone extensions [#permalink]  09 Jun 2009, 15:29
one more way....
let digit4 = 6, the 3! is the way to arrange rest 3 digit, so total 6 ways
let digit4 = 2, the 3! is the way to arrange rest 3 digit, so total 6 ways

so total 12 ways (C)
Re: telephone extensions   [#permalink] 09 Jun 2009, 15:29
Similar topics Replies Last post
Similar
Topics:
If all of the telephone extensions in a certain company must 7 22 Jan 2005, 13:03
If all of the telephone extensions in a certain company must 8 17 Oct 2006, 10:58
If all of the telephone extensions in a certain company must 3 27 Jan 2007, 06:58
If all of the telephone extensions in a certain company must 4 20 Apr 2007, 09:22
A company assign a unique 3 digit telephone extension to 3 11 Mar 2008, 07:07
Display posts from previous: Sort by