Hello Sourabh,

Consider an equilateral triangle of side a. Point A and B have charges +q where A has -2q charge. The system as two dipoles with p1 and p2 along BA and CA respectively. 

The angle between the dipole moment is 60 degree.

The resultant dipole moment(P): root(P^2+P^2+2PCos60*) = root(3P)

where P = qa.

Dipole Moment, P = root(3qa)