A balloon has a circumference of 11 cm. Use the circumference to approximate the surface area of the balloon to the nearest square centimeter.

C = 2 (pi) (r) so 11 = 2 (pi) (r) if you divide 11 by 2 (pi) using pi as 3.14 you get r = 1.752 then plug in the number to S. A. = 4 (pi) r^2 you will get approximately 38.55 sq. Cm of surface area.

Try 38.465cm I'm not good at math but its the best I could do