When Wang Hong reads a book, she reads 25% of the whole book on the first day, and 25 pages on the second day. How much? How many pages does this book have? Please fill in a condition on the horizontal line in the question and answer it.
王红看一本书，第一天看了全书的25%，第二天看了25页，多少，这本书有多少页？请你在题中的横线上填上一个条件，并解答．
<result>50</result>