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1 đầu tàu kéo 1 đoàn tàu chuyển động từ A đến B trong 15 phút vận tốc 30 km/h tại B đoàn tàu được mắc thêm toa và do đó chuyển động đều từ ga B đến C với vận tốc nhỏ hơn trước 10 km/h . Thời gian đi từ ga B đến ga C LÀ 30 phút .tính công của đầu tàu đã sinh ra biết rằng lực kéo của đầu tàu ko đổi là 40 000 N
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Education is an important issue for many people in the UK as well as around the world. In most countries pupils who attend secondary schools take an exam to get a school leaving certificate. One particular worry is why boys are doing so badly. Some twenty years ago, exam scores of girls and boys in a class were compared. Boys got better results in exams, so various steps were taken to improve the results of girls, including having single sex girl-only classes. Now, the situation is reversed, with girls getting better scores than boys. So, what has gone wrong with boys, and what can be done about it? John Dunsford, leader of the Association of Head Teachers in Secondary Schools, says that the fact that boys do not achieve much academically has its roots in society rather than the classroom. Girls, more than boys, see education as a passport to a good job. On the other hand, according to Penny Lewis, a head teacher, young men are not confident enough and are often uncertain about their place in society. Some boys grow up in families where there is no father, which means no male role model to follow. Moreover, boys learn in a different way to girls, preferring small amounts of work with short deadlines rather than large projects extended in time. And education is not seen as "cool". This is not just a problem in Britain. In a study by the Organization for Economic Cooperation and Development and UNESCO, girls did better than boys at reading at the age of 15 in all 45 countries. The UK took the ninth place among the 45 countries in reading skills, although pupils in the UK spend less time reading than in most other countries. Interestingly, the study suggested that British children read for pleasure more often than those in other countries. 23. Twenty years ago, ………………………….. . A. boys didn't do very well in exams. B. school authorities decided to change the situation. C. girls had very good results in exams. D. all pupils went to single-sex classes. 24. Girls have better exam results than boys because ……………………… A. boys are too sure of themselves. B. girls think that a good education will help them find a job. C. boys come from a different place in society than girls. D. girls grow up in complete families. 25. Boys differ from girls in ………………………… . A. the number of books they read. B. the time spent surfing the Internet. C. the way they spend their free time. D. the way they learn. 26. The study by UNESCO showed that British children at the age of fifteen ………………….. A. read a lot although they don't have to. B. spend more time reading than children in other countries. C. are the best at reading. D. can't read very well. 27. The text is mainly about …………………………… . A. the kind of exams pupils take. B. boys' and girls' success in education. C. the educational system in Britain. D. what pupils read for pleasure.

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