SOLUTION: Please help me! This is really hard and I don't know how to do it. Help would be MUCH appreciated! "Find the surface area of a sphere that has a diameter of 4 cm."/ A.64&#960

Algebra ->  Surface-area -> SOLUTION: Please help me! This is really hard and I don't know how to do it. Help would be MUCH appreciated! "Find the surface area of a sphere that has a diameter of 4 cm."/ A.64&#960      Log On


   

Question 473725: Please help me! This is really hard and I don't know how to do it. Help would be MUCH appreciated!
"Find the surface area of a sphere that has a diameter of 4 cm."/
A.64π cm2
B. 32/3 pi cm^3.
C. 4 pi cm^2
D. 16 pi cm^2"



THANK YOU!!!

Found 2 solutions by ccs2011, Theo:
Answer by ccs2011(207) About Me  (Show Source):
You can put this solution on YOUR website!
Surface Area of sphere is 4%2Api%2Ar%5E2
Radius is exactly half the diameter.
Given: diameter is 4 --> %281%2F2%29%2A4+=+2
So the radius of the sphere is 2.
Now substitute this value into general formula
4%2Api%2A2%5E2+=+4%2Api%2A4+=+16%2Api
Therefore, surface area is 16pi sq.cm.

Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
the formula for the surface area of a sphere is 4*pi*r^2
if the diameter is 4 cm, then the radius is 2 cm.
plug that into the equation to get:
surface area of the sphere = 4*pi*2^2 = 4*pi*4 = 16*pi square cm.
square cm is also shown as cm^2.
your answer would be selection D (16*pi*cm^2).