There are 720 books in Xiaojun's house, which are placed on 4 bookshelves, each with 3 floors. How many books are placed on each shelf on average?
小军家有720本书，放在4个书架上，每个书架有3层．平均每个书架每层放多少本书？
<gadget id="calculator">720 / 4 / 3</gadget>
<output>60</output>

<result>60</result>