Total surface area of hollow hemisphere is equal to
Let R ans r be the outer and inner radii of the hemisphere.
Now,its curved surface area=outer surface area+inner surface area
$2R^{2}\times2r^{2}$
$=2\pi (R^{2}+r^{2})sq.units$
$Total surface area=outer surface area+inner surface area+Area at the base$
$=2\pi R^{2}+2\pi r^{2}+\pi (R^{2}-r^{2})$
$=2\pi (R^{2}+r^{2})+\pi(R+r)(R-r)sq.units$
$=\pi(3R^{2}+r^{2})sq.units$