Smith Engineering is in the process of reviewing the salaries of their surveyors. During this​ review, the company found that an experienced surveyor can survey a roadbed in 6 hours.

Question

An apprentice surveyor needs 9 hours to do the same stretch of road. With both how long it takes them to complete the job.

Answer 1

I like to think about these problems in terms of rates per hour

Experienced = 1 road/ 6 hours = .16667 roads per hour

Apprentice = 1 road/ 9 hours = .11111 roads per hour

Now the two rates can be added to find the combined rate E+A = .16667 +.11111 = .27778 roads per hour

Finally, since the question asks how long to finish a road together we need to take the reciprocal of roads per hour to get hours per road

1 /(.27778 roads per hr) = 3.60 hours per road

3.60 hours to finish the road together

I hope that helps!