Answer
The density of the neutron star is $5.4 \times 10^{17}~kg/m^3$
This is much larger than the density of a white dwarf (about $10^9~kg/m^3$) and similar in density to nuclear matter (about $10^{18}~kg/m^3$).
Work Step by Step
$\rho = \frac{mass}{volume}$
The mass of the neutron star is 1.5 times the mass of the sun:
$m = 1.5\times (2.0\times 10^{30}~kg) = 3.0 \times 10^{30}~kg$
We can calculate the volume of the neutron star:
$V = \frac{4}{3} \pi (1.1 \times 10^4~m)^3 = 5.6\times 10^{12}~m^3$
We can use the mass and the volume to find the density $\rho$:
$\rho = \frac{3.0 \times 10^{30}~kg}{5.6\times 10^{12}~m^3} = 5.4 \times 10^{17}~kg/m^3$
The density of the neutron star is $5.4 \times 10^{17}~kg/m^3$
This is much larger than the density of a white dwarf (about $10^9~kg/m^3$) and similar in density to nuclear matter (about $10^{18}~kg/m^3$).
