3. In the plane, a parabola divides the plane into two parts, two parabolas can divide the plane into at most seven parts. Then 10 parabolas can divide the plane into $\qquad$ parts.
3. 191 .

Let $n$ parabolas divide the plane into $a_{n}$ regions. When adding another parabola to maximize the number of regions, this new parabola intersects each of the $n$ given parabolas at 4 points, thus the $n+1$ parabolas are divided into $4n+1$ segments, each of which splits an original region into two. This leads to the recurrence relation $a_{n+1}=a_{n}+4n+1$, and $a_{1}=2$. From this, we can derive $a_{n}=2n^{2}-n+1$. For $n=10$, $a_{10}=191$.