The educational printing factory needs to bind a batch of books. On the first day, 3/8 of these books are bound, and another 300 books are bound on the second day. At this time, the ratio of the number of bound books to the number of unbound books is 7 : 5. How many volumes are there in this batch of books?
教育印刷厂要装订一批图书，第一天装订了这批图书的(3/8)，第二天又装订了300册，这时已装订的册数与未装订的册数的比是7：5．这批图书共有多少册？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">(7/12) - (3/8)</gadget>
<output>5/24 = around 0.208333</output>

<gadget id="calculator">300 / (5/24)</gadget>
<output>1_440</output>

<result>1_440</result>