Inventory valuation choices ripple through the income statement, the balance sheet, and the tax bill, yet most teaching treatments collapse the topic into a single worked example under rising prices and leave students unable to reason about how the choice would change if conditions did. This paper offers two contributions. First, we formalize the six combinations of inventory system (periodic, perpetual) and cost flow assumption (first-in, first-out [FIFO], last-in, first-out [LIFO], weighted average) as a compact mathematical model and apply that model to a single normalized transaction dataset under three price regimes: rising, falling, and stable. The result is a side-by-side comparison of cost of goods sold, ending inventory, and gross profit across all eighteen cases, with the perpetual LIFO worked example completed and the periodic LIFO arithmetic corrected. Second, we synthesize pedagogical evidence on blended learning, visual aids, collaborative learning, classroom technology, and accounting education-specific effectiveness research, showing how instructors could translate that synthesis into concrete classroom materials such as a spreadsheet template or a reproducible Python notebook. The paper positions inventory valuation at the operations-finance interface and points to current data-driven inventory work as the bridge from accounting mechanics to supply chain decision-making.