Xiaohua reads a story book, and reads 15 pages on the first day, and 20 pages on the second day. At this time, he reads exactly 20% of the whole book. How many pages does this book have?
小华看一本故事书，第一天看了15页，第二天看了20页，这时正好看了全书的20%，这本书共有多少页？
<gadget id="calculator">15 + 20</gadget>
<output>35</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">35 / (1/5)</gadget>
<output>175</output>

<result>175</result>