AMC 8 2013 Problem 7
AMC8 2013 年第 7 题
比与比例★★☆☆☆
Trey and his mom stopped at a railroad crossing to let a train pass. As the train began to pass, Trey counted 6 cars in the first 10 seconds. It took the train 2 minutes and 45 seconds to clear the crossing at a constant speed. Which of the following was the most likely number of cars in the train?
Trey 和他妈妈为了让一辆火车通过，在铁路的交叉口停了下来。当火车开始通过时，在前 10 秒他们数到了 6 节车厢。火车以恒定的速度完全通过这个交叉口耗时 2 分钟 45 秒，那么这列火车最有可能有多少节车厢？
- A.60
- B.80
- C.100
- D.120
- E.140
正确答案 · Correct Answer
C
解析 · Solution
Solution 1
Clearly, for every 5 seconds, 3 cars pass. It's more convenient to have everything in seconds: 2 minutes and 45 seconds seconds. We then set up a ratio: 3(165)=5x
2 minutes and 45 seconds is equal to . Since 6 cars pass at around 10 seconds, there are about groups of 6 cars. There are about , so the closest answer choice is 100. P.S: If you got this wrong or wasted time on this question, don't worry. I did too. -PearlSeal34
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