Li Yao read a story book, and read 100 pages in 4 days, accounting for (2/5) of the book. How many pages does the book have?
李瑶读一本故事书，4天读了100页，占这本书的(2/5)，这本书一共有多少页？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">100 / (2/5)</gadget>
<output>250</output>

<result>250</result>