This question is something to do with radian measure. I've never studied this before (I understand a few of the formulas generally used with no idea how they are applied) and want to solve this question:
Two points P and Q lie on a circle with centre O. The radius of the circle is r cm and angle POQ = radians. The length of the arc PQ is 6 cm and the area of the sector PQ is .
Find the values of r and . 
Any help towards answering this is greatly appreciated.
You're told the radius is and that the length of the arc is .
Therefore the angle , in radians, is .
The area of a sector, if the angle is given in radians, is
We know that and that the area is .
From this, we can see .