6.2 Inventory Cost Determination Methods The owner of Aman's Party Supplies was exploring which inventory cost formula to use when costing inventory using the perpetual system. The owner was surprised to find the ending inventory value using the weighted average cost formula was less than the ending inventory value using FIFO. How could this be possible? this would happen because FIFO uses per unit costs from the last purchases to value ending inventory while weighted average uses per unit costs from all the purchases this would happen because FIFO uses per unit costs from the first purchases to value ending inventory while weighted average uses per unit costs from all the purchases it is not possible-ending inventory should have the same value regardless of the cost formula used the FIFO cost formula assigns costs to ending inventory based on the actual physical flow of goods while the weighted average formula uses an estimated flow of goods