Let $x$ be the number of boys. Then we have the number of girl v/s girl matches as $x(2x-1)$, boy v/s boy matches as $x(x-1)/2$, and the number of girl v/s boy matches as $2x^2$. If the number of girls winning in the last kind of matches is $\alpha$, then the ratio condition translates to $32 \alpha = x(11-x)$, so $x=11$ by looking at the highest power of $2$. So $33$ players took part in this tournament.

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