Question

9. The total surface area of sphere is 4πr²? and total surface area of
hemisphere is 3πr²?. Why it is 3πr²? instead of 2
πr² ? Explain.
​

Answer 1

Answer:

The total surface area of a sphere is 4πr² yes you are right there. But the reason why total surface area of a hemisphere is 3πr² you have to imagine a hemisphere. There is a curved surface and a circle at the bottom. The area of the curved surface is 1/2×4πr²=2πr² but for total surface area the area of the bottom circle must also be added. I e 2πr²+πr²=3πr²

Answer 2

ʙᴇᴄᴀᴜsᴇ ᴛʜᴇ ʜᴇᴍɪsᴘʜᴇʀᴇ ʜᴀs ᴀ ᴄɪʀᴄᴜʟᴀʀ ʀᴇɢɪᴏɴ ᴀᴛ ᴛʜᴇ ᴛᴏᴘ, ᴡʜᴏsᴇ ᴀʀᴇᴀ ɪs ɢɪᴠᴇɴ ʙʏ πʀ^2, ᴡʜɪᴄʜ ᴀᴅᴅs ᴜᴘ ᴡɪᴛʜ 2πʀ^2 ᴀɴᴅ ɢɪᴠᴇs 3πʀ^2

ʜᴏᴘᴇ ʏᴏᴜ ɢᴇᴛ ɪᴛ ᴡᴇʟʟ ⛄