If a book costs $15 and you buy 4, what is the total cost?

To find the total cost of purchasing 4 books, you need to multiply the cost of each individual book by the number of books you are buying. In this case, each book costs $15.

The calculation is as follows:

Total cost = Price per book × Number of books

Total cost = $15 × 4

Total cost = $60

Thus, the correct answer is $60, which corresponds to the first choice. This reflects the straightforward multiplication of the price per item by the quantity, making it a fundamental arithmetic operation.