Here we are given Central angle theta as 5pi/3 and radius is 9 in.
Now the formula to find arc length s is given by:

s=θ*r
So the measure of arc length is product of central angle theta and radius of the circle r.
Plugging the value of theta and r here:
s=(5π/3) * 9
s=41.7
Answer: The measure of arc is 41.7 .