When Xiaofang reads a book, the ratio of the number of pages she has read to the number of pages she has not read is 2:5. It is known that she has read 40 pages, and how many more pages will be needed to read half of the book.
小芳看一本书，已看页数与未看页数的比是2：5，已知已看了40页，要再看多少页才看完全书的一半．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">40 / (2/5)</gadget>
<output>100</output>

<gadget id="calculator">40 + 100</gadget>
<output>140</output>

<gadget id="calculator">140 / 2</gadget>
<output>70</output>

<gadget id="calculator">70 - 40</gadget>
<output>30</output>

<result>30</result>