[填空题]
A university library has tw3cbs faga6:o: ;vf3 f.:c emlsa,x6d io sections, one - hx2p6h ij 6ia;qpxa5for books and the other for journals. The probability that a randomly observed visitor accesses the books section is 0.85 , and the probability that ip;xha5ijh -2 x 6paq6the visitor accesses the journals section is 0.3 . Assume that in each visit, visitors access at least one of the two sections.
1. Find the probability that a randomly chosen visitor
1. Accesses both the books and journals section,
2. Only accesses the journals section.
On a typical day, 120 visitors visit the library.
2. On a typical day, find
1. The expected number of visitors to access the books section,
2. The probability that more than 40 visitors access the journals section.
It is found that 70 % of the visitors to the library are students, and that 82 % of these students access the book's section when they visit the librar.≈
3. 1. A library visitor is chosen at random. Find the probability that the visitor is a student and accesses the book's section.
2. A non-student visitor is chosen at random. Find the probability that the visitor accesses the book's section.
