AAPL wrote:Official Guide



If the circle above has center O and circumference 18Ï€, then the perimeter of sector RSTO is
$$A.\ 3\pi+9 \,\,\,\,\,\,\,\, B.\ 3\pi+18 \,\,\,\,\,\,\,\, C.\ 6\pi+9 \,\,\,\,\,\,\,\, D.\ 6\pi+18 \,\,\,\,\,\,\,\, E.\ 6\pi+24$$

\[\left. \begin{gathered}
?\,\,\, = \,\,\,2R + \frac{{60}}{{360}}\left( {2\pi R} \right)\,\,\,\, \Rightarrow \,\,\,\,\,\boxed{\,\,? = 2R\,\,\left( {1 + \frac{\pi }{6}} \right)\,\,\,}\,\,\, \hfill \\
2\pi R = 18\pi \,\,\,\,\mathop \Rightarrow \limits^{:\,\,\pi } \,\,\,\,2R = 18 \hfill \\
\end{gathered} \right\}\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,?\,\, = \,\,\underleftrightarrow {18\left( {1 + \frac{\pi }{6}} \right)}\,\, = \,\,18 + 3\pi \]

Please note that even in a trivial problem like this one, we never forget the main motto of our method:

Present FOCUS and DATA in an structured way and CONNECT them as soon as possible!

Regards,
fskilnik.