Answer
$$\frac{{16\pi }}{9}{\text{radians}}$$
Work Step by Step
$$\eqalign{
& {\text{We know that }}{{\text{1}}^ \circ } = \frac{\pi }{{180}}{\text{radians}}{\text{. Thus}}{\text{,}} \cr
& {320^ \circ } = 320\left( {\frac{\pi }{{180}}} \right){\text{radians}} \cr
& {\text{Multiplying}} \cr
& {320^ \circ } = \frac{{320\pi }}{{180}}{\text{radians}} \cr
& {320^ \circ } = \frac{{16\pi }}{9}{\text{radians}} \cr} $$