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

 It is currently 27 May 2015, 12:41

### 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

# use 26 character to make 3 characters password, only mid

Author Message
TAGS:
Manager
Joined: 22 Apr 2003
Posts: 180
Followers: 1

Kudos [?]: 8 [0], given: 0

use 26 character to make 3 characters password, only mid [#permalink]  03 Dec 2003, 16:48
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
use 26 character to make 3 characters password, only mid figure should be not tha same as the other two, ask number of password?

from China's site
Intern
Joined: 22 Nov 2003
Posts: 41
Location: Serbia
Followers: 0

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

Number of passwords without "middle character" rule:
26*26*26

then we have to subtract number of forbidden passwords :

char X char (char = X ( only one character or both of them) )

there are 26*3 passwords like those mentioned above,
each of characters (26 ) has three forbiden passwords...when X is at first place of the password , when X is at last place and when is X at both places.
e.g. Forbiden passwords for letter A:
A A char
char A A
A A A

Finally, number of possible passwords is :
26 * ( 26*26 - 3 ) = 17 498

Senior Manager
Joined: 11 Nov 2003
Posts: 355
Location: Illinois
Followers: 1

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

should this be calculated like this?

Total number = 25 x 26 x 25 = 16,250
Intern
Joined: 22 Nov 2003
Posts: 41
Location: Serbia
Followers: 0

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

I am not sure...where did I make mistake?
My way is indirect, your solution is direct and easier..but I am not sure now what is right answer...
Intern
Joined: 22 Nov 2003
Posts: 41
Location: Serbia
Followers: 0

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

I got it...there are not only 26 x 3 forbidden passwords...
A A char - 25
char A A - 25
A A A -1
multiplied by 26 ..26 x ( 26+25).....=1326
too complicated...
Well, it seems that I should go to sleep know...my brain doesn't work well anymore...it's 4 a.m. in my country
Bye!
SVP
Joined: 03 Feb 2003
Posts: 1608
Followers: 6

Kudos [?]: 78 [0], given: 0

my solution:

the total number is 26*26*26
the number of wrong combinations is 26*25*1

so, [26*26*26]–[26*25]=16926
Senior Manager
Joined: 02 Mar 2004
Posts: 329
Location: There
Followers: 1

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

Re: PS [#permalink]  17 May 2004, 17:26
chihao wrote:
use 26 character to make 3 characters password, only mid figure should be not tha same as the other two, ask number of password?

case1: XYZ, where X and Z are the same.
26*25
case2: XYZ, where letters X and Z are different.
26*25*24

OR:
Lets fix Y: this can be in 26 ways.
X and Z are different from Y: This can be done in 25*25 ways.

Re: PS   [#permalink] 17 May 2004, 17:26
Similar topics Replies Last post
Similar
Topics:
A four-character password consists of one letter of the alphabet 1 03 Mar 2015, 14:36
B-Schools distinctive characters 4 19 Apr 2013, 12:23
3 The uniqueness of the Japanese character is the result of 15 30 Jul 2012, 12:25
The uniqueness of the Japanese character is the result of 4 18 Nov 2011, 13:04
A four character password consists of one letter and three 1 11 Sep 2005, 09:52
Display posts from previous: Sort by