Two spheres of the same density have a ratio of 9 to 16 in surface area. If the small sphere weighs 15 kg, what does the large sphere weigh?

Surface area of a sphere = 4 pi r^2

radius of small sphere = sqrt (9/4pi) = 0.8463

radius of larger one = sqrt (16/4pi) = 1.1284

ratio of the weights is 1.1284^3 : 0.8463^3 = 2.37

large sphere weighs 15 * 2.37 = 35.55 kg