For a book, I read 25% of the whole book on the first day and 40% of the whole book on the second day. I read a total of 195 pages in two days. Do you know how many pages this book has?
一本书，第一天看了全书的25%，第二天看了全书的40%，两天共看了195页，你知道这本书有多少页吗？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/4) + (2/5)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">195 / (13/20)</gadget>
<output>300</output>

<result>300</result>