Sponsored Ad:
Results 1 to 7 of 7

Thread: (n - 1)! Rule

  1. #1
    Within my grasp! forgmat's Avatar
    Join Date
    Sep 2004
    Location
    India
    Posts
    101
    Rep Power
    16


    Good post? Yes | No

    (n - 1)! Rule

    Sponsored Ad:
    Anyone knows more about it. Please explain.
    GMAT D-Day: 640! (43/35/5.0)

    TOEFL: 280 (6.0 in Essay)

  2. #2
    only Loeb spaces! reactor's Avatar
    Join Date
    Dec 2004
    Posts
    2,080
    Rep Power
    30


    Good post? Yes | No

    Re: (n - 1)! Rule

    This is factorial and means (n-1)(n-2)(n-3).........[n-(n-2)][n-(n-1)] = (n-1)!
    i.e 5! = 1 x 2 x 3 x 4 x 5 = 120 6!/5! = 6 in the same way (n-1)! can be expressed as n!/n
    Factorials are widely used in Combinatorics to calculate probabilities.
    "It's easy to have faith in yourself and have discipline when you're a winner, when you're number one. What you've got to have is faith and discipline when you're not yet a winner." Vince Lombardi

    How to write a lazy proof

    Teaching yourself how to prove

  3. #3
    I will charanya's Avatar
    Join Date
    Dec 2004
    Location
    USA
    Posts
    389
    Rep Power
    17


    Good post? Yes | No

    Re: (n - 1)! Rule

    252^5 divisible by 6^n .what is n?
    Need stepwise explanation please.

  4. #4
    Trying to make mom and pop proud
    Join Date
    Nov 2004
    Posts
    19
    Rep Power
    16


    Good post? Yes | No

    Re: (n - 1)! Rule

    Quote Originally Posted by charanya
    252^5 divisible by 6^n .what is n?
    Need stepwise explanation please.
    Hi Charanya,

    Ur question is not clear to me . I guess u r missing some part of question.

    If I solve above problem I get various answers....0,1,2,3,4,5,6 etc....there is no specific answer so this can't be a GRE question

  5. #5
    Eager!
    Join Date
    Oct 2004
    Posts
    36
    Rep Power
    16


    Good post? Yes | No

    Re: (n - 1)! Rule

    252^5 = (2^2 * 3^2 * 7)^5 = 6^10 * 7^5
    6^10 * 7^5 % 6^n = 0 (divisible) when n = [0,10]
    Is this correct

  6. #6
    I will charanya's Avatar
    Join Date
    Dec 2004
    Location
    USA
    Posts
    389
    Rep Power
    17


    Good post? Yes | No

    Re: (n - 1)! Rule

    which is the greatest value of n that makes 252^5 divisable by 6^n??
    I'm i clear now?

    Ya, ans is 10 .but iam not able to understand u.

  7. #7
    Trying to make mom and pop proud
    Join Date
    Nov 2004
    Posts
    19
    Rep Power
    16


    Good post? Yes | No

    Re: (n - 1)! Rule

    252^5=(7x6^2)^5=(7^5)x(6^2)^5
    =(7^5)x(6^10)
    252^5 is divisible by 6^10 hence n=10

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Banana Rule (SCN Rule): Exceptions
    By Erin in forum Reference
    Replies: 10
    Last Post: 09-16-2019, 08:13 AM
  2. 3/2 rule - Help
    By psriniva in forum GMAT Sentence Correction
    Replies: 3
    Last Post: 10-23-2008, 08:31 AM
  3. Banana Rule (SCN Rule)
    By Erin in forum Reference
    Replies: 3
    Last Post: 04-27-2007, 05:18 AM
  4. RULE OF 3 & RULE OF 5??
    By coolmavs in forum GRE Math
    Replies: 0
    Last Post: 09-04-2005, 01:17 AM
  5. "THAT" Rule
    By mohamed in forum TOEFL Grammar
    Replies: 3
    Last Post: 01-18-2003, 02:53 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •