SOLUTION: What is the radius of a tennis ball with a surface area of 28 in.²? A. 1.5 in. B. 1.8 in. C. 2.1 in. D. 2.4 in.

Algebra ->  Surface-area -> SOLUTION: What is the radius of a tennis ball with a surface area of 28 in.²? A. 1.5 in. B. 1.8 in. C. 2.1 in. D. 2.4 in.      Log On


   

Question 261344: What is the radius of a tennis ball with a surface area of 28 in.²?
A. 1.5 in.
B. 1.8 in.
C. 2.1 in.
D. 2.4 in.
Found 2 solutions by Edwin McCravy, nerdybill:
Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!
What is the radius of a tennis ball with a surface area of 28 in.²?

A tennis ball is a sphere.  The formula for the surface area of a sphere is

A+=+4pi%2Ar%5E2

We substitute 28 for A and solve for r

28+=+4pi%2Ar%5E2

Divide both sides by 4pi

28%2F%284pi%29+=+r%5E2

7%2F%28pi%29+=+r%5E2

Take the square root of both sides:

sqrt%287%2Fpi%29=+r

Punch that out on a calculator and you
get 1.49270533 inches, which rounds to 
1.5 inches, choice A.

Edwin

Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
surface area of any sphere is 4(pi)r^2
.
4(pi)r^2 = 28
(pi)r^2 = 7
r^2 = 7/(pi)
r = sqrt(7/(pi))
r = 1.5 inches