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Legenda o medvjedu | Brother bear #4

Nešto me vuče na put, na put...

Koda i Kenai su krenuli na put. Da ubije dosadu, Koda je sa sobom ponio 100 špagica, koje naravno sve skupa imaju 200 krajeva. Koda zatim 100 puta nasumično bira dva kraja, moguće i od iste špagice, te ih veže skupa (dva odabrana kraja su onda nadalje neupotrebljiva u igri).

Koji je očekivani broj petlji kad Koda završi igru? U formalnom jeziku vjerojatnosti, ako je L broj petlji, odredi E[L].

(Petlja je skup povezanih špagica. Na slici ispod možete vidjeti primjer dvije petlje od tri špagice.)

Attachment petlja.png

Tell everybody I'm on my way...

Koda and Kenai are going on an adventure. To cure his boredom, Koda brought 100 strings, which of course have 200 ends. Koda then randomly pairs two ends together, possibly from the same strings, and ties them together (the chosen two ends cannot be used again in the game). He repeats this process 100 times until all string ends are used.

What is the expected number of loops when Koda finishes his game? In the formal language of probability, if L is the number of loops, calculate E[L].

(A loop is a set of connected strings. On the image below, you can see an example of two loops made out of three strings.

Attachment petlja.png