A book has 100 pages, read 20%, how many pages have been read.
一本书有100页，看了20%，看了多少页．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 * (1/5)</gadget>
<output>20</output>

<result>20</result>