Read a book, read 25% of it on the first day, and read 150 pages on the second day. At this time, the ratio of those who have read to those who have not read is 1:1. How many pages are there in this book?
看一本书，第一天看了它的25%，第二天又看了150页，这时已看与未看的比是1：1，这本书共有多少页？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/4) - (1/2)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">150 / (1/4)</gadget>
<output>600</output>

<result>600</result>