[tex]\begin{array}{|c|ll} \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\stackrel{\textit{48\% of 560}}{\left( \cfrac{48}{100} \right)560}\implies 268.8~\hfill \approx 268~boys[/tex]