There are 3 bookshelves, and each shelf has 5 floors. A total of 450 books are placed. How many books are placed on each floor.
有3个书架，每个书架有5层，共摆放了450本书，每层摆放多少本书．
<gadget id="calculator">450 / 3 / 5</gadget>
<output>30</output>

<result>30</result>