Xiaoxiao read an extra-curricular book. On the first day, I read 25% of the total pages. On the second day, I read (4/5) of the first day. I read exactly 45 pages in two days. How many pages are there in this extra-curricular book? Page?
笑笑读一本课外书，第一天读了总页数的25%，第二天读了第一天的(4/5)，两天正好读了45页，这本课外书一共有多少页？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/4) * (4/5)</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">45 / (9/20)</gadget>
<output>100</output>

<result>100</result>