There are 5,400 original literature books and science books in the school library, among which science books are less than literature books (1/5). Recently, I bought a batch of science and technology books. At this time, the science and technology books are literary books (9/10). How many science and technology books did the school library buy?
学校图书室原有文艺书和科技书共5400本，其中科技书比文艺书少(1/5)．最近又买入一批科技书，这时科技书是文艺书的(9/10)．学校图书室又买入多少本科技书？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 + (4/5)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">5_400 / (9/5)</gadget>
<output>3_000</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">3_000 * (9/10)</gadget>
<output>2_700</output>

<gadget id="calculator">3_000 - 2_700</gadget>
<output>300</output>

<result>300</result>