# Discrete math

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

1. ### mrburnerRon 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_CoolNever 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. ### mrburnerRon Paul 2008

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

4. ### mrburnerRon 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_PreludeThere might not be an "I" in the word "Team", but

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Ooo! Ooo! I know! I know!

6. ### crotchfruitGuest

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

worst class ever.

7. ### 5Gen_PreludeThere might not be an "I" in the word "Team", but

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And yet you use it everyday!

8. ### mrburnerRon Paul 2008

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so...can you help me out?

9. ### 5Gen_PreludeThere 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. ### NolanTAYou 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. ### mrburnerRon 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-FASTOT Supporter

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Do you still need help?

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