甲、乙两个工程队共同完成一项工程需16天，现两队合作9天，甲队被调走，乙队又单独工作了21天才完成，问：甲、乙两队单独工作各需几天完成？
设甲队单独做需x天完成．
依题意得：
+(9 16
-1 16
)×21=1．1 x
解这个方程得：x=24．
经检验：x=24是原方程的解．
当x=24时，
-1 16
=1 x
，1 48
=48．1
-1 16 1 x
答：甲、乙两队单独工作分别需24天、48天．
Read the following text and choose the most suitable heading from the list A-F for each paragraph. There is one extra heading which you do not need.
小题1: It's something that most of us find annoying. We're on our way home after a hard day at school and trying to have a quiet chat with a classmate or get in a little reading, when our peace is disturbed by someone screaming into their cell phone: "I'M ON THE BUS !" 小题2: A survey published last week suggests Americans do not like the impolite use of today's electronic communication gadgets. Besides noisy phone users, sending and receiving e-mails while in company are also as very poor manners, reports MSNBC.com. 小题3: One of the practices that participants in the survey most objected to was the use of phones, iPods and other devices during religious festivals. Some 90 per cent of those surveyed thought this was insensitive and disrespectful. 小题4: The website quotes Dr Genevieve Bell, conductor of the survey and director of Intel's User Experience Group as saying: "Theses are issues about common sense." But she believes that the rights and wrongs of the public use of technology are still in the process of formation. 小题5: The survey does suggest, according to MSNBC, that most Amencans accepted that the technologies are a fact of modern life. They had nothing against the use of laptops and cell phones in bathrooms. And an electronic thank-you note was just as acceptable as a handwritten one. |