Capacity rate = 100 customers/hour Input Rate Customers/hour Time 12pm 2pm 10am 150 200 100 50 Capacity rate = 100 customers/hour Inventory Waiting Customers Time 200 100 12pm 2pm 10am 300

Capacity rate = 100 customers/hour Input Rate Time 12pm 2pm 10am 50 200 100 Customers/hour 150 Capacity rate = 100 customers/hour 6pm Inventory Waiting Customers Time 200 100 12pm 2pm 10am 6pm

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What is the average inventory? Time 200 100 12pm 2pm 10am Inventory 6pm From 10am to 6pm the inventory is: 0 units x 2 hrs. + 100 units x 6 hrs 8hrs =75 units on average

What is the average wait time? Take 1 200 100 12pm 2pm 10am Inventory Time 12pm 2pm 10am 50 200 100 Customers/hour 6pm For the units that wait (12pm to 6pm) INV = 100 units TH = (200 units/hr x 2 hr + 50 units/hr x 4 hr)/6 hr = 100 units/hr FT = INV/TH = 100units / 100 units/hr = 1 hr For all units (10am to 6pm) INV = 75 units TH = (50 x 2 + 200 x 2 + 50x 4 )/8 = 87.5 units/hr FT = INV/TH = 75/87.5 = 0.857 hr

What is the average wait time? Take 2 12pm 2pm 10am 50 200 100 Customers/hour Time 200 100 12pm 2pm 10am Inventory 6pm 2 hr wait 1 hr wait on average The 100 units arriving from 10am to 12 pm wait 0 minutes. A unit arriving at 12pm waits 0 minutes. A unit arriving at 2pm waits 200 units / 100 units/hr = 2 hrs. A unit arriving at 6pm waits 0 minutes. Average waiting time for the 400 units arriving from 12pm to 2 pm = 1 hr. Average waiting time for the 200 units arriving from 2pm to 6pm = 1 hr. All 600 units arriving from 12pm to 6pm wait 1 hr on average. Weighted average waiting time is (100 x 0 hr + 600 x 1hr) / 700 = 0.857 hr.

Total Waiting Time TH = 700 units/day Average waiting time = 0.857 hr Total waiting = 700 x 0.857 hr = 600 unit – hr / day Or if just considering units that wait TH=600 units Average waiting time = 1 hr Total waiting = 600 x 1 hr = 600 unit – hr / day

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