For a novel, Xiao Ming reads (1/5) of the whole book on the first day, and the rest (1/5) on the second day, and has not read the rest of the book.
一本小说，小明第一天看了全书的(1/5)，第二天看了剩下的(1/5)，还剩下全书的多少没有看．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) * (4/5)</gadget>
<output>16/25 = around 0.64</output>

<result>16/25 = around 0.64</result>