There is a batch of books that sold 400 copies on the first day, 1/3 of the total number on the second day, 25% of the total number on the third day, and 150 books left. How many books are there in this batch?
有一批书，第一天卖出400本，第二天卖出总数的(1/3)，第三天卖出总数的25%，还剩150本，这批书有多少本？
<gadget id="calculator">400 + 150</gadget>
<output>550</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/3) - (1/4)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">550 / (5/12)</gadget>
<output>1_320</output>

<result>1_320</result>