In Module D, we will learn more about Little's Law (page 763 in 12th edition of book), as it applies to queuing theory. Generally, Little's Law is: Number of Units = Rate (as expressed in units per given time period) x Time

or "The average number of some item in a system equals its average arrival rate multiplied by the average time each unit spends in the system." (Practical Operations Management, 2nd edition 2017, Simpson and Hancock, Hercher Publishing Inc., pages 432 and 489).

This can be stated as: Inventory (the overall amount of some item in a system) = its average arrival rate (driven by demand) multiplied by the average time it spends in the system: I=lambda T or I = RT

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Alternatively, Inventory = RT, or Inventory = Flowrate x Flowtime

If a company had 100 units in inventory in their production system (WIP) and the flowtime is 20 hours, what is the flowrate (in units per hour)?