Ans: B
Note that the possible greatest length of the thin string is $25.5\mbox{ m}$. Note also that the possible smallest length of the little sting is $4.5\mbox{ cm}$.
Note that the possible greatest length of the thin string is $25.5\mbox{ m}$. Note also that the possible smallest length of the little sting is $4.5\mbox{ cm}$.
Hence, we have
$\begin{array}{cl}
& 2550 \div 4.5 \\
= & 566.667
\end{array}$
Therefore, the greatest possible value of $n$ is $566$.
