Fourth grade mathematics: knowledge bookstore carries out promotional activities. For every book in 25 yuan, buy 5 books and get 1 book. If you buy 40 books, how much will it cost? How much cheaper is each book?

Buy 5 books and get 1 book. If you buy 40 books,

* * * How much?

40/6 = 6+4

25×30+25×4 = 850 yuan.

How much cheaper is each book?

25-850/40 = 3.75 yuan