A book with 400 pages, Xiao Wang read it in 5 days (1/5), according to this calculation, how many days will he have to finish it.
一本书400页，小王5天看了(1/5)，照这样计算，他还要多少天才能看完．
<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">(1/5) / 5</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">400 * (1/25)</gadget>
<output>16</output>

<gadget id="calculator">(4/5) / 16</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">400 * (1/20)</gadget>
<output>20</output>

<result>20</result>