11. Find the value of
$$
\frac{2006^{2}-1994^{2}}{1600} .
$$
11. Ans: 30
$$
\begin{aligned}
\frac{2006^{2}-1994^{2}}{1600} & =\frac{(2006+1994) \times(2006-1994)}{1600} \\
& =\frac{4000 \times 12}{1600} \\
& =30 .
\end{aligned}
$$