There are 15 bookshelves in a library, each shelf has 3 floors, and 120 books are placed on each floor, how many books can be placed in total?
一个图书室有15个书架，每个书架有3层，每层放120本书，一共能放多少本书？
<gadget id="calculator">120 * 3 * 15</gadget>
<output>5_400</output>

<result>5_400</result>