# Tagged Questions

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### probability equiprobable space?

For the problem below are we going to use the equiprobable space. Which is In particular, if S contains n points then the probability of each point is 1/n . For an event A, P(A) = number of elements ...
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### How many way can we obtain $0$?

You are walking in road and you have only two directions,forward and back.Your $n$th step has length $n$. How many way can you return your starting point after $n$ steps ? It is equivalent to say ...
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### Calculating $\binom{1}{2}$

Show $\displaystyle\sum_{i=1}^{n} \binom{i}{2}=\binom{n+1}{3}$. I'm thinking right now (though not getting anywhere with it) that I want to expand out the summation portion to $i!/2!(i-2)!$ and ...
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### How many handshakes [duplicate]

Image text: The Handshake Puzzle: There are four married couples who attend a party hosted by Mr. and Mrs. Smith. Several handshakes take place (but no one shakes their own hand or their ...
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### Is there a relation that is irreflexive, anti-symmetric and not transitive?

from the set $\{a, b, c, d\}$? Of the one's I have tried, it at best is two of the three, but never all.
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### combinatorics questions from studying

Hi all I need some assistance How many 5-digit briefcase combinations contain 1.Two pairs of distinct digits and 1 other distinct digit. (e.g 12215) I wasn't sure on which approach was correct. 10 ...
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### General (Set Builder) definition for a relation composed with itself n times

Questions What does the set builder notation for $S\circ R$ look like? I'm having the most trouble knowing when there is too much information or not enough information on either side of the 'such ...
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### How do I find “at most” x bit strings of length 20?

I tried searching online and I found several examples of doing such problems, but I'm still not sure if I'm doing them correctly and would greatly appreciate some help! How many bit strings of length ...