How Do You Determine Time in an RC Circuit for Charge and Current Changes?

[wildredhead]

Homework Statement

The capacitor in an circuit is initially uncharged
In terms of R and C, determine the time required for the charge on the capacitor to rise to 50% of its final value.

In terms of R and C, determine the time required for the initial current to drop to 10% of its initial value

Homework Equations

I know i need to use Q=CV(1-e^-t/RC)
But I don't know how to put it all together.

The Attempt at a Solution

 

[tiny-tim]

Hi wildredhead!

(try using the X² tag just above the Reply box )

I know i need to use Q=CV(1-e^-t/RC)
But I don't know how to put it all together.

Show us how far you've got, and where you're stuck, and then we'll know how to help!