jmc

Let the hemisphere's radius be $r$. The hemisphere's base is a circle with radius $r$; thus, we have $\pi r^2=100\pi$. Taking the positive solution for $r$ yields $r=10$. The surface area of the curved part of the hemisphere is half the surface area of a sphere with radius 10, which is $\frac{1}{2}\cdot 4\pi (10^2)=200\pi$. The total surface area of the hemisphere is the sum of this curved surface area and the base area, which is $200\pi +100\pi =\boxed{300\pi }$.