Could you please help with these three math pages.

Each of 10000 shelves in a certain library is 300 cm long. to estimate how many books in the library need rebinding, a librarian takes a sample of 50 books using the following procedure: he first generates a random integer between 1 and 10,000 to select shelf and then generates a random number between 0 and 300 to select a location on that shelf. thus a pair of random numbers (2531,25.4) would tell the librarian to include the book that is above the location 25.4 cm from the left end of shelf number 2531 in the sample.