The school assigns some books to students in grade five and grade six according to the ratio of 5:9. It is known that grade six gets 160 more books than grade five, so how many books are there in total?
学校将一些图书按5：9分别五、六两个年级的学生阅读，已知六年级比五年级多分得160本，那么这些图书共有多少．
<result>640</result>