Asubtending arc on a circle with a radius of 4.5 centimeters has an arc length of 8π. the measure of the angle subtended by the arc is what?

For the answer to the question above, 

the angle of 360 ° → π.d 

the angle of x ° → 8π 

You make the cross-multiply and you can get: 

x * π.d = 8π * 360 

x * d = 8 * 360 

x = 8 * 360/d → where d = 2r 

x = 8 * 360/2r 

x = 4 * 360/r → where r = 4.5 cm 

x = 4 * 360/4.5 

x = 320 °