The school library bought 840 books and put them on 6 bookshelves, each with 5 floors. How many books are placed on each floor on average?
学校图书馆买来840本书，放在6个书架上，每个书架有5层．平均每层放了多少本书？
<gadget id="calculator">840 / 6 / 5</gadget>
<output>28</output>

<result>28</result>