The teacher wants to put 780 books on 2 bookshelves on average, and each bookshelf has 3 floors. How many books are placed on each floor on average?
老师要把780本图书平均放在2个书架上，每个书架有3层，平均每层放多少本书？
<gadget id="calculator">780 / 2 / 3</gadget>
<output>130</output>

<result>130</result>