Xiaohua reads an extra-curricular book, and has already read 25% of the whole book, which is exactly 30 pages. How many pages does this book have? (Solve the equation.)
小华看一本课外书，已经看了全书的25%，正好是30页．这本书有多少页？(用方程解．)
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 / (1/4)</gadget>
<output>120</output>

<result>120</result>