Question 9
Three-digit powers of $2$ and $5$ are used in this “cross-number” puzzle. What is the only possible digit for the outlined square? $$
\begin{array}{lcl} \textbf{\text{ACROSS}} & & \textbf{\text{DOWN}} \\ \textbf{2. } 2^m & & \textbf{1. } 5^n \end{array}
$$
\begin{array}{lcl} \textbf{\text{ACROSS}} & & \textbf{\text{DOWN}} \\ \textbf{2. } 2^m & & \textbf{1. } 5^n \end{array}
$$