I was reviewing corporate finance and doing some questions in the book and realize that they give us two different equations to calculate # of days in inventory, # of days of receivables, and # of days of payables.

In financial statement analysis p. 351 and 352.

Inventory Turnover = COGS / Avg Inv DOH = # days in period / Avg Inventory

Corporate Finance: P. 205 Problem 2:

For the solution they use ending inventory as the numerator (under the impression it should be avg inventory since they give both beg and end amounts) / (COGS/365). Now I realize that the calculation is the same, even though they use a different equation, but it confuses me as to why they are using the ending invenory vs the average inventory.