Ding Ding reads a story book. He reads 25% of the whole book on the first day, and 140 pages on the second day. The rest (2/5) of the book has not been read. How many pages does this book have?
丁丁读一本故事书，第一天读了全书的25%，第二天读了140页，还剩下全书的(2/5)没有读，这本书共有多少页？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/4) - (2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">140 / (7/20)</gadget>
<output>400</output>

<result>400</result>