The total number of people circulating is equal to the average number of people circulating in public libraries multiplied by the number of libraries multiplied by the number of months. Borrowing number/total book collection = book borrowing rate, which refers to the ratio of the number of books borrowed by readers to the number of books borrowed by readers within a certain time range, that is, the average number of books borrowed by each reader throughout the year. A library is an institution that collects, sorts out and collects books and materials for people to read and refer to.