Hi guys, I'm not sure if I'm going about this the correct way, but it seems to be the only one that makes sense right now. The problem reads: Io, a satellite of Jupiter, has an orbital period of 1.77 days and an orbital radius of 4.22E5 km. From these data, determine the mass of Jupiter. So, with that in mind, the equation that pops out at me is T^2 = (4*pi^2)(a^3)/(G*M_big_). Now, assuming that M_big_ is the size of jupiter, one can solve for M_big_: M_big_ = (4*pi^2)(a^3)/(T^2*G). Before substituition, I convered 1.77 days into 1.53E5 seconds. Then, I substituted: M_big_ = ((4*pi^2)*(4.22E5km)^3)/((1.53E5)^2)*(6.67E-11) = 1.07E7 kg. So, is my process right and I'm simply punching it in wrong, or is it that my logic is flawed? Thanks!