The library bought 240 new books. Put it on 3 bookshelves on average, and each bookshelf has 4 floors. How many books are placed on each floor on average?
图书馆新买图书240本．平均放在3个书架上，每个书架有4层．平均每层放多少本？
<gadget id="calculator">240 / 3 / 4</gadget>
<output>20</output>

<result>20</result>