batch of textbooks will be shipped in the new semester. A total of 250 textbooks are needed for the fifth and sixth grades. The ratio of the number of textbooks required for the fifth and sixth grades is 12:13, and the textbooks for the sixth grade account for (1/5) of this batch of books. How many books are there in total?
新学期运来一批课本，五、六年级共需要250本，五、六年级所需课本数的比是12：13，六年级的课本占这批书的(1/5)．这批书共有多少本？
<gadget id="calculator">12 + 13</gadget>
<output>25</output>

<gadget id="calculator">250 / 25</gadget>
<output>10</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">13 / (1/5)</gadget>
<output>65</output>

<gadget id="calculator">10 * 65</gadget>
<output>650</output>

<result>650</result>