1, a book "Education of Love" by 8 yuan. Xinhua Bookstore is having an activity. Buy 3 copies and get 1 copy. Buy four copies at a time. How much cheaper is each book?

2. An encyclopedia 55 yuan. During the National Day, Wanlian Shopping Plaza held promotional activities, buying four sets and getting one free. Teacher Xia bought four sets at a time, so how much cheaper is each set than usual?

3. During the National Day, Blue Sky Shopping Mall launched a "buy one get one free" promotion, and bought air conditioners to send rice cookers worth 85 yuan. The mall * * * sold 105 air conditioner. How much did you earn during the activity?

4. For every New Year calendar in 20 yuan, buy 4 copies and get 1 copy. Li Ming bought 34 copies at a time. How much did he pay less for a copy?

5. A pair of ping-pong bats 14 yuan, buy five and get two free, and buy five pairs at a time. How much cheaper is each pair?