For a book, Xiao Ming read 20% of the book on the first day, the remaining 30% on the second day, and how much of the book he read on the second day.
一本书，小明第一天读了这本书的20%，第二天读了余下的30%，第二天读了这本书的多少．
<gadget id="calculator">20 / 100</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">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(4/5) * (3/10)</gadget>
<output>6/25 = around 0.24</output>

<result>6/25 = around 0.24</result>