College Physics (4th Edition)

$2.6N$
The weight is prorportional to the mass and inversely proportional to the square of the radius, so W is proportional to $\frac{m}{r^{2}}$ Forming a proportion, we have $\frac{Wj}{We}=\frac{mj}{me}\times (\frac{re}{rj})^{2}=320\times\frac{1}{11^{2}}=\frac{320}{121}$ On Jupiter, the apple would weigh = $\frac{320}{121}\times1N=2.6N$