There are 480 books in the school library, which are placed on 4 shelves on average, and each shelf has 6 floors. How many books are placed on each floor on average?
学校图书馆有480本书，平均放在4个书架上，每个书架有6层．平均每层放书多少本？
<gadget id="calculator">4 * 6</gadget>
<output>24</output>

<gadget id="calculator">480 / 24</gadget>
<output>20</output>

<result>20</result>