Assume that protons and neutrons have equal masses. Mass of a...

As we know, $\text{density of nuclei} = \dfrac{\text{mass of nuclei}}{\text{volume of nuclei}}$

$⇒ ρ = \dfrac{1 . 6 \times {10}^{- 27}A}{\dfrac{4}{3}\pi{\left(1 . 5 \times {10}^{- 15}\right)}^{3}A}$

$= \dfrac{1 . 6 \times {10}^{- 27}}{14 . 14 \times {10}^{- 45}} = 0 . 113 \times {10}^{18}kg{m}^{- 3}$

We also know that, density of water is ${ρ}_{w} = {10}^{3}kg{m}^{- 3}$.

Hence,
$\dfrac{ρ}{{ρ}_{w}} = 11 . 31 \times {10}^{13}$.

Therefore, $n \approx 11$