Congcong reads a book, and has read 40% of the whole book, and he has not read the rest of the book.
聪聪读一本书，已经读了全书的40%，还剩这本书的多少没有读．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>