Final answer:
The cost of the inventory on January 31, under the FIFO method, is $3,285.
Step-by-step explanation:
The cost of the inventory on January 31, under the FIFO (First-In, First-Out) method can be calculated by determining the cost of the units sold first. Since Partridge Bookstore does not maintain perpetual inventory records, we assume that the 365 units on hand on January 31 are the units sold during January. The cost of these units can be calculated by finding the product of the number of units sold and the cost of the earliest units purchased.
In this case, we start with the 500 units on hand at January 1, costing $9 each. So, the cost of the units sold is 365 units x $9 = $3,285.
Therefore, the cost of the inventory on January 31, under the FIFO method, is $3,285.