Answer:
the magnitude of the force is 192.29 N
Solution:
As per the question:
Charges present on the corner of the triangle are same, Q =

Since, its an equilateral triangle, distance between the charges, l = 0.50 m
Now,
The Coulomb force on a charge due to the other is:

where
K = Coulomb constant =



The the net force on the charges in an equilateral triangle on all the charges due to each other:
