Xiaoqiang especially likes to read "Children's Encyclopedia". He read 120 pages in 4 days, and read it for another 20 days before finishing the book. How many pages are there in this book?
小强特别喜欢看《少儿百科全书》，他4天看了120页，像这样又看了20天，才把这本书看完．这本书一共多少页？
<gadget id="calculator">120 / 4</gadget>
<output>30</output>

<gadget id="calculator">4 + 20</gadget>
<output>24</output>

<gadget id="calculator">30 * 24</gadget>
<output>720</output>

<result>720</result>