A book, read 8 pages a day, and read (2/5) of this book in 4 days. At this speed, how many days can I finish the whole book?
一本书，每天看8页，4天看了这本书的(2/5)，照这样的速度，全书几天可以看完？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) / 4</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / (1/10)</gadget>
<output>10</output>

<result>10</result>