There are $5$ girls and $5$ boys in a chess club. the club holds a round-robin tournament in which every player plays against every other player exactly once. in how many games does a girl play against another girl?

Let's call the five girls .

Since every player plays against every other player exactly once, has to play against . This are four maches.

has already played against , so she has to play against . This are three matches.

has already played against , so she has to play against . This are two matches.

has already played against , so she has to play against . This is one match.

So, the total is matches.

step-by-step explanation:

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