A librarian put 39 books back on the shelves before lunch. Of the books, 13 were non-fiction. What is the ratio of the number of non-fiction books to the total number of books the librarian put away before lunch?

Answer 1

The number of fiction books is 39 - 13 = <<39-13=26>>26 books.
The ratio of non-fiction books to the total number of books is 13/39 = <<13/39=1/3>>1/3. Answer: \boxed{\frac{1}{3}}.