Xiaojun reads a story book for 8 days, 20 pages a day, and reads it for another day, which is exactly half of the book. How many pages does this book have? (Solve with a comprehensive formula)
小军看一本故事书，看了8天，每天看20页，再看1天就正好是这本书的一半，这本书有多少页？(用综合算式解答)
<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 20 * 2</gadget>
<output>360</output>

<result>360</result>