Point a and b lie on a circle with a radius of 1, and arc ab has a length pi/3. what fraction of the circumference of the circle is the length of arc ab?

First we need to find the circumference of the circle with the formula C=2*r*π, where r is the radius and it is r=1. So C=2*1*π=2π. The arc AB has a length of π/3. To find the fraction of the circumference the arc has we just divide the length of the arc AB with the circumference C:
AB/C=(π/3)/(2π)=π/(6π)=1/6. So the length of the arc AB is 1/6 of the circumference C.