Question

Ruby red paint costs $0.50 per square inch. A ball is painted ruby red and costs $100.00 to paint. What is the diameter of the ball? Round to the nearest tenth of an inch.

Answer 1

Assumes:  ball is equivalent to spherical shape

Find surface area (painted):
($100.00)/($0.50 / in²) = 200 in²

Surface area of sphere:
SA = 4πr²

(200 in²) = 4πr²

r² = (200 in²)/(4π) = 15.91549431 in²

r = √(15.91549431) = 3.989422804 in

diameter = 2r = 2(3.989422804 in) = 7.978845608 in

Rounded to the nearest tenth of an inch:

d = 8.0 inches

 . . .  answer is . . . diameter = 8.0 inches