If you read 40 pages of a book on the first day and the rest (2/5) on the second day, the number of pages you have read is equal to the number of pages you have not read. How many pages are there in this book?
一本书，第一天看了40页，第二天看了余下的(2/5)，这时已看的和未看的同样多，这本书共有多少页？
<gadget id="calculator">40 * 2</gadget>
<output>80</output>

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

<gadget id="calculator">40 * (2/5) * 2</gadget>
<output>32</output>

<gadget id="calculator">80 - 32</gadget>
<output>48</output>

<gadget id="calculator">(2/5) * 2</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2 - (4/5) - 1</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">48 / (1/5)</gadget>
<output>240</output>

<result>240</result>