There were 320 science and technology books in the school library last year, and some more were bought this year. This year, there are 400 science and technology books in total. What percentage has the number of science and technology books this year increased compared to last year?
学校图书馆去年有320本科技书，今年又买来一些，今年共有400本，今年的科技书比去年增加了百分之几？
<gadget id="calculator">400 - 320</gadget>
<output>80</output>

<gadget id="calculator">80 / 320</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>