Question 283947
10 patients in 5 hours, so if the doctor had 40 patients, that is 4 times the amount of patients from before, well if you multiply 4 by 5hrs that equals 20hrs. 
10 patients = 5 hours
20 patients = 10 hours
30 patients = 15 hours
40 patients = 20 hours

For each increment of 10 patients, add 5 hours.

Comes out to, 40 patients in 20 hours.