Zhang Ling reads a story book. On the first day, she read 40% of the whole book. On the second day, she read 10 more pages than on the first day. She just finished reading it. How many pages does this book have?
张玲看一本故事书，第一天看了全书的40%，第二天比第一天多看了10页，正好看完，这本书有多少页？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">10 / (1/5)</gadget>
<output>50</output>

<result>50</result>