An automated car wash serves customers with the following serial process: pre-treat, wash, rinse, wax, hand dry. Each of these steps is performed by a dedicated machine except for the hand dry step, which is performed manually on each car by one of 4 workers. The steps of the process have the following processing times:
(a) Pre-treat: 4 minute per car
(b) Wash: 3 minutes per car
(c) Rinse: 2 minutes per car
(d) Wax: 2 minutes per car
(e) Hand dry: 14 minutes per car

If the car wash has a demand of 16 cars per hour, what is the flow rate of the process?

Flow rate is  = 15 cars/hour

Explanation:

For the flow rate of the process the following calculations are made:

hand dry: 14 minutes per car = 60 divided by14 = 4.29 cars/ hour (Rounded off)

(60 is the number of minutes in one hour)

but hand dry has 4 workers = 4.29 multiply by 4 = 17 cars/hour (Rounded off)

Pre-treat takes 4 minutes per car, rate = 60 divided by 4 = 15 cars/hour

wash takes 3 minutes per car, rate = 60 divided by 3 = 20 cars/hour

we do not need to check the other processes since the they all take less time than pre-treat

Flow rate is minimum of all = 15 cars/hour