3 point charges on the vertices of an equilateral triangle

[Unemployed]

Homework Statement

3 equal point charges on the vertices of a triangle. If the each of the charges are doubled, why is the resulting force on each charge quadrupled?

Homework Equations

F= Fx +Fy

F= kqk2/r^2

The Attempt at a Solution

I got doubled

 

[housemartin]

well the force acting on charged particle (Coulomb's law) is equal to:
F=k\frac{q_1 q_2}{r^2}
if distance is left same, and charges is doubled, you get:
F=k\frac{2q_1 2q_2}{r^2}=4k\frac{q_1 q_2}{r^2}
so the force is bigger four times