The printing factory needs to pack a batch of books. If there are 40 books in each box, there are exactly 25 boxes. Now it needs to pack 20 books in each box. How many boxes should be packed?
印刷厂要包装一批书，如果每箱40本，正好有25箱，现在要包装成每箱20本，要包装多少箱？
<gadget id="calculator">40 / 20</gadget>
<output>2</output>

<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<result>50</result>