Question

9. The total surface area of sphere is 4nr’ and total surface area of
hemisphere is 3Tr?. Why it is 3itrº instead of 21tr?? Explain.​

Answer 1

Answer:

you are wrong here, see steps below.

Step-by-step explanation:

TSA(sphere) = 4 x pi x r x r = CSA(sphere)

{because sphere is totally curved. hence, TSA = CSA}

CSA(hemisphere) = (4 x pi x r x r) / 2 = 2 x pi x r x r

TSA(hemisphere) = CSA(hemisphere) + base(hemisphere)

= (2 x pi x r x r) + (pi x r x r)

= (3 x pi x r x r)

Answer 2

Your statement :-

The total surface area of sphere is 4$\pi$$r^2$ and total surface area of

hemisphere is 3$\pi$$r^2$.

What went wrong?

It is 3π$r^2$ instead of 2π$r^2$.

Reason:-

The total surface area of sphere is 4$\pi r^2$ and if you split it into two, both each would have 2$\pi r^2$ lateral surface area plus a circular base  $\pi r^{2}$.

Now adding both up gives

$2\pi r^2+\pi r^2=3\pi r^2$.