The printing factory wants to pack a batch of books. If each pack contains 40 books, it needs to pack 18 packs. If each pack contains 30 books, how many packs should it pack? (Solve with ratio)
印刷厂要将一批图书打包，如果每包40本，要装18包，如果每包30本，要装多少包？(用比例解)
<gadget id="calculator">40 * 18</gadget>
<output>720</output>

<gadget id="calculator">720 / 30</gadget>
<output>24</output>

<result>24</result>