Question

A spherical balloon has a circumference of 23 cm. What is the approximate surface area of the balloon to the nearest square centimeter? (1 point)
674 cm2
415 cm2
168 cm2
1,662 cm2

Answer 1

168cm2
Let r cm be the radius of the balloon, then 
2pi(r)=23=>r=23/(2pi) 
The surface area= 
4pi(r^2)= 
4pi[23/2pi)]^2= 
(23^2)/pi=168.386 cm^2 
approximately.