Medal + fan:
A spherical balloon has a circumference of 19cm. What is the approximate surface area of the balloon to the nearest square cm?
A 115cm^2
B 460cm^2
C 361cm^2
D 1,134cm^2

Question

love_333 · Answer

@Erak ?

erak · Answer

So first solve for your radius when given circumference.

C = 2pi(r)

love_333 · Answer

r=3.02 so 3

love_333 · Answer

right?

erak · Answer

yeah, not rounding and leaving it as like 9.5/pi could help a little.

erak · Answer

So just stick that radius into the SA of a sphere formula

SA = 4pi(r)^2

love_333 · Answer

Okay with sticking to 9.5 I got 1,133.54

erak · Answer

oh it's "9.5/pi", so in your calc it's

SA = 4pi(r)^2
SA = 4pi(9.5/pi)^2

love_333 · Answer

If I do the first one i get: 1,133.54
If i do the second i get: 114.9098

love_333 · Answer

Which is it..?

erak · Answer

the second one, r = 9.5/pi, which is equivalent to like 3.02 ish, just that having an exact radius will help.

answer is A

love_333 · Answer

Okay. Thank you!