Describe costing inventory using first-in, first-out. Address the different treatment, if any, that must be given for periodic and perpetual inventory updating. Describe costing inventory using last-in, first-out. Address the different treatment, if any, that must be given for periodic and perpetual inventory updating. Describe costing inventory using weighted average. Address the different treatment, if any, that must be given for periodic and perpetual inventory updating. What insights can be gained from inventory ratio analysis, such as inventory turnover ratio and number of days sales in inventory ratio?