There is a batch of books in the school. If each class is divided into 45 books, it can be distributed to 20 classes. If each class gets 50 books, how many classes can it be distributed to?
学校有一批图书，如果每班分45本，正好可以分给20个班．如果每班分得50本，可以分给几个班？
<gadget id="calculator">20 / 50</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">45 * (2/5)</gadget>
<output>18</output>

<result>18</result>