Question

If two solid-hemisphere s of same base radius r are joined together along their bases , then curved surface area  of this new solid is 

Options

• \[4 \pi r^2\]

• \[6 \pi r^2\]

• \[3 \pi r^2\]

• \[8 \pi r^2\]

Answer 1

Base radius of the hemisphere = r
Since the two hemispheres are joined end to end, it becomes a complete sphere. 
Curved surface area of the new solid = total surface area of the sphere.

\[\text { Curved surface area of the new solid } = 4 \pi r^2\]