The total surface area of a hemisphere of radius `r` is `pir^2` (b) `2pir^2` (c) `3pir^2` (d) `4pir^2`

Explanation

The surface area of a sphere of radius `r \is\ 4pir^2`
Half of this is `2pir^2`
If you have a hemispherical object then it has a base which is a circle of radius `r.`
The area of a circle of radius `r \is\ pir^2`
So the hemisphere is meant to include the base then the surface area is `2pir^2+pir^2=3pir^2`