11. (3 points) Cutting a cake, cutting 1 time can make at most 2 pieces, cutting 2 times can make at most 4 pieces, cutting 3 times can make at most 7 pieces, continuing this way, cutting 5 times can make at most $\qquad$ pieces.
【Solution】Solution: When cutting 1 time, the number of pieces is $1+1=2$ pieces; when cutting 2 times, the number of pieces is $1+1+2=4$ pieces;

when cutting 3 times, the number of pieces is $1+1+2+3=7$ pieces;
$\qquad$
when cutting $n$ times, the number of pieces $=1+(1+2+3 \cdots+n)=1+\frac{n(n+1)}{2}$. Therefore, when cutting 5 times, the number of pieces is $1+\frac{5 \times 6}{2}=16$ pieces; hence the answer is: 16.