The Hectora's rate of work in part per hour is 18 hours
Given the following parameters:
Taking the sum of the reciprocals of the time taken;
1/6 = 1/9 + 1/r
1/r = 1/6 - 1/9
1/r = 9-6/54
1/r = 3/54
Cross multiply
3r = 54
r = 54/3
r = 18 hours
Hence the Hectora's rate of work in part per hour is 18 hours
Learn more about reciprocals here: https://brainly.com/question/2534506