# Homework Help: Simple electric field strength problem

1. Apr 30, 2014

### liamporter1702

1. The problem statement, all variables and given/known data

How far away from a 360μC charged particle is the electric field strength 49mN/C?

2. Relevant equations
E=(8.99x10$^{9}$ x $\frac{Q}{r^{2}}$

3. The attempt at a solution
I assumed it would be a simple case of rearranging the equation to give r=$\sqrt{\frac{8.99x10^{9}xQ}{E}}$ but after doing this and subbing in the values I got a value of 8127, which is clearly not correct. The answer that has been given is 186mm but I can't see the solution.

2. Apr 30, 2014

### liamporter1702

Could it be a case of the answer given is not correct?