c.s.a of a hemisphere

Question

Here is a question which I would like to understand. I want to know

How to prove that c.s.a of a hemisphere is $2\pi r^2$ ?

I'm a 10th CLASS average student,so please keep it simple.

Thank you....

Answer 1

We know that C.S.A of a sphere is $4\pi r^2$. Therefore C.S.A of hemisphere is $2\pi r^2$.