8. In $\mathrm{Rt} \triangle A B C$, there is a point $M$ on the right-angle side $A B$ and a point $P$ on the hypotenuse $B C$. It is known that $M P \perp B C$, the area of $\triangle B M P$ is 
equal to half the area of quadrilateral MPCA, $B P$ 
$=2$ cm, $P C=3$ 
cm. Then the area of $\mathrm{Rt} \triangle A B C$ is 
square cm.
8. $\triangle M B P \subset \triangle C B A$,
$$
\begin{array}{l}
S_{\triangle M B P}: S_{\triangle C M A}=1: 3, \\
B P: B A=1: \sqrt{3}, \\
\therefore B A=2 \sqrt{3}, \\
A C=\sqrt{13} . \\
S_{\triangle A B C}=\frac{1}{2} \times 2 \sqrt{3} \times \sqrt{13}=\sqrt{39} .
\end{array}
$$