Xiao Ming reads a book. He reads 20% of the book on the first day, and (1/4) of the book on the second day. As a result, he reads 72 pages in two days. How many pages does this book have?
小明看一本书，第一天看了这本书的20%，第二天看了这本书的(1/4)，结果两天看了72页．这本书共有多少页？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/5) + (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">72 / (9/20)</gadget>
<output>160</output>

<result>160</result>