Two different planets have same density but different radii. The acceleration due to gravity (g) on the surface of the planets is dependent on its radius (R) as.

$g \propto \frac{1}{R^2}$ $g \propto R^2$ $g \propto \frac{1}{R}$ $g \propto R$

$g \propto R$

$g=\frac{G M}{R^2}=\frac{G\left(\frac{4 \pi R^3}{3}\right) \rho}{R^2}$ $\Rightarrow g=\frac{4 \pi R G \rho}{3}$