11. (3 points) If the value of the expression $(\square+121 \times 3.125) \div 121$ is approximately 3.38, then the natural number that should be filled in $\square$ is $\qquad$
【Solution】Let $\square=x$, then:
$$
\begin{array}{l}
(x+121 \times 3.125) \div 121, \\
=(x+121 \times 3.125) \times \frac{1}{121}, \\
= \frac{1}{121} x+121 \times 3.125 \times \frac{1}{121}, \\
= \frac{1}{121} x+3.125 ; \\
\frac{1}{121} x+3.125 \approx 3.38, \\
\frac{1}{121} x \approx 0.255, \\
0.255 \times 121=30.855 ; \\
x= 30 \text { when, } \frac{1}{121} x=\frac{1}{121} \times 30 \approx 0.248 ; \\
x=31 \text { when, } x=\frac{1}{121} \times 31 \approx 0.255 ;
\end{array}
$$

When $x=31$, the result of the operation is 3.38.
Therefore, the answer is: 31.