Six point masses each of mass ‘m’ are placed at the vertices of a regular hexagon of side $l$.  The force acting on any of the masses is

lets assume their are 6 point sized masses,

The magnitude of gravitational force on A due to B, F is given by ${\mathrm{F}}_{\mathrm{ABorAF}}=\frac{\mathrm{Gmm}}{(\mathrm{AB}{)}^2}=\frac{\mathrm{Gmm}}{{\mathrm{l}}^2}$.

The magnitude of gravitational force on A due to C,E is given by ${\mathrm{F}}_{\mathrm{ACorAE}}=\frac{\mathrm{Gmm}}{(\mathrm{AE}{)}^2}=\frac{\mathrm{Gmm}}{(\sqrt{3}\mathrm{l}{)}^2}=\frac{{\mathrm{Gm}}^2}{3{\mathrm{l}}^2}$

The magnitude of gravitational force on A due to D is given by ${\mathrm{F}}_{\mathrm{AD}}=\frac{\mathrm{Gmm}}{(\mathrm{AD}{)}^2}=\frac{\mathrm{Gmm}}{(2\mathrm{l}{)}^2}=\frac{{\mathrm{Gm}}^2}{4{\mathrm{l}}^2}$

$\text{ Resultant force due to }{\mathrm{F}}_{\mathrm{AB}}\text{ and }{\mathrm{F}}_{\mathrm{AF}}\text{ is }{\mathrm{F}}_{\mathrm{R}1}=\frac{{\mathrm{Gm}}^2}{l^2}\text{ along }\mathrm{AD}$

$\text{ Resultant force due to }{\mathrm{F}}_{\mathrm{AC}}\text{ and }{\mathrm{F}}_{\mathrm{AE}}\text{ is }{\mathrm{F}}_{\mathrm{R}2}=\frac{{\mathrm{Gm}}^2}{\sqrt{3}{\mathrm{l}}^2}\text{ along }\mathrm{AD}$. 

Net force acting on A along AD is given by ${\mathrm{F}}_{\mathrm{R}}={\mathrm{F}}_{\mathrm{R}1}+{\mathrm{F}}_{\mathrm{R}2}+{\mathrm{F}}_{\mathrm{AD}}=\frac{{\mathrm{Gm}}^2}{l^2}+\frac{{\mathrm{Gm}}^2}{\sqrt{3}{l}^2}+\frac{{\mathrm{Gm}}^2}{4l^2}$

Net force acting on A= $\frac{G{m}^2}{l^2}\left[\frac{{\displaystyle 5}}{{\displaystyle 4}}+\frac{{\displaystyle 1}}{{\displaystyle \sqrt{3}}}\right]$