The surface area of a sphere is found using the formula SA=4πr^2, where r is the radius. If the surface area of a sphere is 144π square feet, what is the radius, in feet?
A.6
B.12
C.18
D.36
Please Help

Question

The surface area of a sphere is found using the formula SA=4πr^2, where r is the radius. If the surface area of a sphere is 144π square feet, what is the radius, in feet?
A.6
B.12
C.18
D.36
Please Help

anonymous · Answer

I'm thinking that it's 18 but i'm not sure

nurali · Answer

4πr^2=144π
r^2=144π/4π
r^2=36
r=6

nurali · Answer

However you cannot have a negative radius so we get rid of the negative one and we are left with

anonymous · Answer

we are left with r=6 right because 
144π=4πr2
divide by 4 pi
36=r^2
square root:
r=±6
we can't have the negative so we end up with
r = 6