Answer
$804.5 Kg/m^3$
Work Step by Step
We can find the required density as follows:
$\rho_L=\frac{(\frac{2\pi}{3}+\frac{\sqrt {3}}{4})r^2}{\pi r^2}\rho_w$
We plug in the known values to obtain:
$\rho_L=\frac{(\frac{2\pi}{3}+\frac{\sqrt 3}{4})r^2}{\pi r^2}(1000Kg/m^3)$
This simplifies to:
$\rho_L=804.5 Kg/m^3$
