Solving for Current Decay in a Resistor/Capacitor Circuit

[fasegovia]

Homework Statement

A fully charged 10e-4 F capacitor has a potential difference across it of 9Volts. It is then connected to a resistor of 10 ohms. How long will it take for the current through the resistor to decrease to 1/2 of its initial value?

Homework Equations

The Attempt at a Solution

I know the answer is 6.9e-4 secs... but I want to know how it was done :/ Anyone?

 

[diazona]

What formulas do you know (or can you look up) that involve a circuit with a resistor and a capacitor?

 

[fasegovia]

Well I have..
V = IR
I = |q|nAv
v = uE

R = L |q|nAu

 

[mugaliens]

http://en.wikipedia.org/wiki/Capacitor#DC_circuits". And solve for t!