Huanhuan reads a book, reads 10% of the whole book on the first day, and the remaining 20% on the second day, and how much of the book he reads on the second day.
欢欢读一本书，第一天读了全书的10%，第二天又读了余下的20%，第二天读了这本书的多少．
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(9/10) * (1/5)</gadget>
<output>9/50 = around 0.18</output>

<result>9/50 = around 0.18</result>