Thread: What is the force of two charged particles?

Two charged particles repel each other with a force f. If the charge of one of the particles is quadrupled and the distance between them is doubled, then the force will be?

I know the equation for this is F= kQ1Q2/ r2. I do have an answer key for this, but I want to be able to understand why the answer is what it is, and how to do this. Can some explain this thoroughly? I don't want to just look at the equations.

F1= kQ1Q2/ r^2
F2= k(4*Q1)Q2/ (2*r)^2

divide: (F2 / F1) = [ k(4*Q1)Q2/ (2*r)^2 ] / [ kQ1Q2/ r^2 ]

you get F2 = F1