Question

Question 15
If two solid hemispheres of same base radius r are joined together along their bases the curved surface area of this new solid is
(A) $4\pi r^2$
(B) $6\pi r^2$
(C) $3\pi r^2$
(D) $8\pi r^2$

Answer 1

Option (A) is correct.

The curved surface area of a hemisphere is $2\pi r^2$ and here, we join solid hemispheres along their bases of radius r, from which we get a solid sphere. Hence, the curved surface area of new solid $=2\pi r^2+2\pi r^2=4\pi r^2$