Teaching and learning process
1. A DVD rental store offers two ways to rent discs: one is to rent discs sporadically, each disc is 1 yuan; The other is membership card rental. The card handling fee is l2 yuan per month, and the rental fee is per card. 0.4 yuan Xiao Bin often comes to the store to rent discs. How many CDs do you rent every month?
2. Liang Xiao bought an energy-saving lamp with 15 watt and an incandescent lamp with 100 watt for 2 yuan. Suppose the service life of two lamps is 2000 hours, and the electricity charge is 0.5 yuan/kWh. When the lighting lasts, the cost of two lamps is the same.
3. (Shunyi District, 20 10) During the May Day, Xiao Ming, Liang Xiao and other students went to the park to play with their parents. The following is a conversation between Xiao Ming and his father when they buy tickets (pictured). Try to answer the following questions according to the information in the picture:
(1) How many adults and students did Xiaoming go to?
(2) Please help Xiao Ming think about which way to buy tickets is more economical?
4. The students of Class 9, Grade 7 in a school bought 50 extra-curricular math books from a publishing house by mail at the price of 7.50 yuan each. According to the regulations of the publishing house, mail order 10 copies or less (including l0 copies) requires an additional mail order fee of 3 yuan; Mail order for more than 10 copies (excluding 10 copies) requires a mail order fee of 15% of the book fee. When sending money through the post office, a remittance fee of 1 yuan is required for each remittance of 100 yuan, and a remittance fee of 100 yuan is required for remittances less than 100 yuan.
(1) After discussion by the class committee, there are two different mail order schemes: the first scheme is to mail l0 copies each time and send them in five times; The second scheme is to order 50 copies by mail at one time, and ask for the cost of two different mail order schemes.
(2) If the number of mail-order books is 60 and 70 respectively, please compare the price difference between each mail-order book and the above two different mail-order schemes to find out the price difference, so as to explain which scheme is more economical.
5. There are two charging methods for surfing the Internet in a certain place, and users can choose one of them: A. Time system: 2.8 yuan/hour, and B. Monthly system: 68 yuan/month. In addition, the communication fee of 1.2 yuan/hour is added for each internet access mode.
(1). A user spends 20 hours on the Internet every month. Which online mode is more cost-effective?
(2) A user spends money online every month 120 yuan. Which method is cost effective?
(3) How long does it take to get online?