A school library has 120 books. Each student needs 5 books for their classes. The library was able to help 4 students on the first day of school, 5 students on the second day and 6 students on the third day. How many students can the library help out on the fourth day of school? Let's be accurate as possible.
On the first day, the library used 4 students * 5 books = 20 books. On the second day, the library used 5 students * 5 books = 25 books. On the third day, the library used 6 students * 5 books = 30 books. On the fourth day, the library had 120 books - 20 - 25 - 30 = 45 books remaining. The library can help 45 books / 5 books = 9 students on the fourth day.
The answer: 9.