There are two layers of books on a bookshelf. There are 60 books on the upper layer and 120 books on the lower layer. 20% of the books on the upper layer are as many as the number of books on the lower layer.
一个书架上有两层书，上层有书60本，下层有书120本，上层书的20%和下层书的多少同样多．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) / 120</gadget>
<output>1/600 = around 0.001667</output>

<gadget id="calculator">60 * (1/600)</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>