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