The school library has 50 science and technology books, 120 literature and art books, 40 information books, and 130 reference books. How many books of each type are there on average?
学校图书室有科技书50本，文艺书120本，信息书40本，工具书130本．平均每种书有多少本．
<gadget id="calculator">50 + 120 + 40 + 130</gadget>
<output>340</output>

<gadget id="calculator">340 / 4</gadget>
<output>85</output>

<result>85</result>