Discrete math

Discussion in 'OT Technology' started by mrburner, Oct 8, 2003.

  1. mrburner

    mrburner Ron Paul 2008

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    i'm working on my homework right now and there is 1 problem i'm having a little trouble with...just wondering if someone can point me in the right direction or possibly unconfuse me...it seems easy, i think i might just be going about it in the wrong way

    question: how many bit strings of length n, where n is a positive integer, start and end with 1s?

    would it just be n/4?
     
  2. Joe_Cool

    Joe_Cool Never trust a woman or a government. Moderator

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    n/4 isn't right. You're sort of on the right track though.

    Think about when n=3. Can you really have .75 different bit strings? Do some trial and error. For any n, there are 2^n possible strings.

    For example, when n=2, there are 2^2 (or 4) possible bit strings:
    00
    01
    10
    11

    and exactly 1 of them begins and ends with 1. Try all the possible combinations when n=3, 4, and 5 and see what you can come up with.

    I really can't give you more without actually giving you the answer.
     
  3. mrburner

    mrburner Ron Paul 2008

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    that is plenty...i was just blanking out on getting started...thanks
     
  4. mrburner

    mrburner Ron Paul 2008

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    ok...just went through the rest and there are a couple others i can't figure out

    1. show that if n is a positive integer, then (2n,2) = 2(n,2) + n^2 by algebraic manipulation

    now when i say (2n,2) i mean
    (2n)
    (2 )

    except in just one pair of tall parenthesis...as in the 2n is above the 2...and same with the n,2

    2. how many subsets with an odd number of elements does a set with ten elements have?

    3. how many ways are there for ten women and six men to stand in a line so that no two men stand next to each other? (hint: first position the women and then consider possible positions for the men)

    this one i am just not sure if my answer is right
    i got 11!/(6!5!)=462...seemed kinda high to me so i just wanted to double check

    thanks for any help in advance
     
  5. 5Gen_Prelude

    5Gen_Prelude There might not be an "I" in the word "Team", but

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    Ooo! Ooo! I know! I know!
     
  6. crotchfruit

    crotchfruit Guest

    memories of discrete math... flooding back.. must.. kill..self.

    worst class ever.
     
  7. 5Gen_Prelude

    5Gen_Prelude There might not be an "I" in the word "Team", but

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    And yet you use it everyday!
     
  8. mrburner

    mrburner Ron Paul 2008

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    so...can you help me out?
     
  9. 5Gen_Prelude

    5Gen_Prelude There might not be an "I" in the word "Team", but

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    I got the same answer doing it a completely different way for 3
     
  10. NolanTA

    NolanTA You talkin' to me? OT Supporter

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    Man, I'm gonna be completely honest with you, I had discrete math probably 10 years ago, and I made it through 1 week before I dropped and changed majors... good luck.
     
  11. mrburner

    mrburner Ron Paul 2008

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    discrete isn't anything compared to my principles of computer organization class...if i was still a freshman or sophmore, i'd be changing majors because of that class
     
  12. FLY-FAST

    FLY-FAST OT Supporter

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    Do you still need help?
     
  13. mrburner

    mrburner Ron Paul 2008

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    no, i got it all figured out...thanks
     

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