Stuck on a radians problem

[Cloe]

a sector OAB has a radius r and area A.
Find the arc length in terms of A and r ?

Plzz help me someone........

[MathsMan]

let the angle at the centre be θ

A=θr/2
θ=2A/r
arc length = θr
= r(2A/r)
=2A/r