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Nguyenbao15122000
2 năm trước
2 xạ thủ đứng đối diện một vách núi. Xạ thủ thứ nhất bắn 1 viên đạn,xạ thủ thứ hai nghe được 2 tiếng nổ liên tiếp cách nhau 2 giây. Tính khoảng cách giữa 2 xạ thủ biết vận tốc truyền âm trong không khí là 330m/giây và điểm mà âm thanh đội lại từ vách núi với 2 xạ thủ tạo thành 1 tam giác đều.
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 ere are many websites on the Internet which provide lists of the world’s best cities to visit, live or work in.  ese lists usually grade the cities in order, from ‘best’ to ‘worst’, and are based on facts and gures provided by local or national organisations.  e City Brands Index (CBI) also provides a list of best and worst cities. However, unlike other surveys, it is based on the idea that cities are similar to products in shops. It asks ordinary people in other countries to grade cities in the same way that they would grade a product, like a so drink or a car. What is particularly di­ erent about the CBI is that the people who take part in the survey may not have ever visited the cities. Instead, they are asked to say what they think the cities are like, basing their opinions on things like news stories, magazine articles or television programmes they have heard or seen. Each year, about 10,000 people in 20 countries take part in the CBI survey, and they grade a total of 50 cities.  ey do this by lling in an online questionnaire.  ere are several categories in the survey.  ese include things like the economy, education, the environment, local culture, climate and what the city’s residents are like.  e CBI list is useful because it helps people choose a good place to live, nd work or take a holiday. It also helps regional governments to understand why people and businesses are, or are not, coming to their cities, and so shows them areas which they could develop or improve. The CBI believes that cities are like 1 which people can buy when they go shopping. Surveys take place every 2 . A maximum of 3 cities are included in the survey. A number of different 4 are included in the survey. The CBI list is helpful for: • people who are trying to decide where to 5 or get a job. • people who are looking for a good 6 destination. • local 7 who want to make their city a better place.

In a recent internet survey, tourists and business travellers were asked to rate 50 cities around the world, from the best to the worst. Of the top three cities, two were in Europe and one was in Australia. In third place was London, scoring highly mainly because it was the most famous city on the list of 50 surveyed. It was also seen as a very good place to do business, and was an important cultural centre. However, it lost points because people believed it was an extremely expensive place to live. Sydney was also a very popular destination, achieving second place on the list because people believed it had the friendliest inhabitants, as well as the best standard of living and the nicest climate. It failed to make the top spot, however, because people thought there were very few things to see there, and many also thought it was too far away from other business and cultural centres. At the top of the list was Paris. Despite problems such as the large amount of traffic, it beat other cities to first place because people considered it to be the most interesting city, with more museums, art galleries and places of interest than anywhere else. People also thought it was the best city to take a holiday in. City Overall position in survey Perceived advantages Perceived disadvantages London 1 • Is more well-known than the other cities. • Has excellent 2 opportunities. Is very 3 . Sydney Second • Residents are the 4 . • Has the best quality of life. • Has the most pleasant 5 . Not many things to see. Paris 6 • Is more 7 than other cities. Has a lot of 8

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