Surface Area of a Hollow Hemisphere

Q. TSA of hollow hemisphere of outer radius R and inner radius r is _______.

1. $\pi (3R^2+r^2)$
2. $3\pi (R^2+r^2)$
3. $2\pi (R^2+r^2)$
4. $\pi (R^2+3r^2)$

Q. If a concentric hemisphere of radius $\frac{R}{2}$ is removed from a radius of hemisphere is $R$. Find the ratio of TSA of remaining to that of CSA of removed.

1. $4.5$
2. $3.25$
3. $6.5$
4. $5$